Add 'test' target to unix/Makefile
Add 'test' target to unix/Makefile

In conjunction with #504 this allows you to do things like:
```shell
make -C unix clean && make -C unix test CC=gcc-4.7
```
all from the top-level micropython directory :-)

Something similar could probably be done for windows/Makefile too, but I don't have a cygwin setup to test with.
redbear/micropython,xuxiaoxin/micropython,alex-robbins/micropython,dxxb/micropython,pfalcon/micropython,infinnovation/micropython,kostyll/micropython,martinribelotta/micropython,micropython/micropython-esp32,blmorris/micropython,xuxiaoxin/micropython,firstval/micropython,tdautc19841202/micropython,rubencabrera/micropython,jlillest/micropython,SHA2017-badge/micropython-esp32,xuxiaoxin/micropython,oopy/micropython,dxxb/micropython,rubencabrera/micropython,utopiaprince/micropython,cloudformdesign/micropython,aethaniel/micropython,tdautc19841202/micropython,xyb/micropython,ChuckM/micropython,tuc-osg/micropython,henriknelson/micropython,pramasoul/micropython,mgyenik/micropython,puuu/micropython,omtinez/micropython,oopy/micropython,pfalcon/micropython,martinribelotta/micropython,chrisdearman/micropython,jimkmc/micropython,heisewangluo/micropython,tdautc19841202/micropython,mgyenik/micropython,slzatz/micropython,mhoffma/micropython,TDAbboud/micropython,supergis/micropython,ericsnowcurrently/micropython,PappaPeppar/micropython,supergis/micropython,vitiral/micropython,pramasoul/micropython,EcmaXp/micropython,lowRISC/micropython,neilh10/micropython,turbinenreiter/micropython,oopy/micropython,noahchense/micropython,bvernoux/micropython,ernesto-g/micropython,trezor/micropython,alex-robbins/micropython,misterdanb/micropython,vitiral/micropython,cwyark/micropython,ganshun666/micropython,redbear/micropython,martinribelotta/micropython,hiway/micropython,utopiaprince/micropython,adamkh/micropython,vriera/micropython,lbattraw/micropython,ChuckM/micropython,tdautc19841202/micropython,ahotam/micropython,aethaniel/micropython,ruffy91/micropython,methoxid/micropystat,matthewelse/micropython,feilongfl/micropython,stonegithubs/micropython,feilongfl/micropython,torwag/micropython,aethaniel/micropython,redbear/micropython,redbear/micropython,praemdonck/micropython,adafruit/micropython,ceramos/micropython,blmorris/micropython,tralamazza/micropython,Vogtinator/micropython,swegener/micropython,xhat/micropython,pramasoul/micropython,blmorris/micropython,AriZuu/micropython,noahchense/micropython,xhat/micropython,alex-robbins/micropython,jlillest/micropython,ryannathans/micropython,redbear/micropython,deshipu/micropython,alex-march/micropython,supergis/micropython,slzatz/micropython,vriera/micropython,turbinenreiter/micropython,jlillest/micropython,selste/micropython,mhoffma/micropython,mpalomer/micropython,puuu/micropython,rubencabrera/micropython,pozetroninc/micropython,pozetroninc/micropython,pfalcon/micropython,kostyll/micropython,drrk/micropython,noahwilliamsson/micropython,adamkh/micropython,noahchense/micropython,MrSurly/micropython-esp32,warner83/micropython,dinau/micropython,Vogtinator/micropython,supergis/micropython,paul-xxx/micropython,turbinenreiter/micropython,hiway/micropython,kostyll/micropython,Timmenem/micropython,drrk/micropython,selste/micropython,ericsnowcurrently/micropython,danicampora/micropython,methoxid/micropystat,oopy/micropython,hosaka/micropython,hosaka/micropython,adafruit/micropython,toolmacher/micropython,suda/micropython,ernesto-g/micropython,aethaniel/micropython,infinnovation/micropython,PappaPeppar/micropython,vitiral/micropython,dmazzella/micropython,jmarcelino/pycom-micropython,firstval/micropython,cwyark/micropython,danicampora/micropython,adafruit/circuitpython,paul-xxx/micropython,dmazzella/micropython,Peetz0r/micropython-esp32,ericsnowcurrently/micropython,deshipu/micropython,tobbad/micropython,chrisdearman/micropython,matthewelse/micropython,torwag/micropython,tralamazza/micropython,skybird6672/micropython,MrSurly/micropython-esp32,ganshun666/micropython,misterdanb/micropython,orionrobots/micropython,dxxb/micropython,jimkmc/micropython,noahwilliamsson/micropython,ernesto-g/micropython,turbinenreiter/micropython,mpalomer/micropython,dinau/micropython,turbinenreiter/micropython,SungEun-Steve-Kim/test-mp,cnoviello/micropython,skybird6672/micropython,TDAbboud/micropython,trezor/micropython,infinnovation/micropython,slzatz/micropython,mgyenik/micropython,vriera/micropython,noahchense/micropython,heisewangluo/micropython,AriZuu/micropython,deshipu/micropython,stonegithubs/micropython,xyb/micropython,jlillest/micropython,utopiaprince/micropython,cnoviello/micropython,emfcamp/micropython,xuxiaoxin/micropython,EcmaXp/micropython,swegener/micropython,lowRISC/micropython,stonegithubs/micropython,EcmaXp/micropython,jmarcelino/pycom-micropython,praemdonck/micropython,paul-xxx/micropython,deshipu/micropython,dmazzella/micropython,mianos/micropython,pramasoul/micropython,omtinez/micropython,EcmaXp/micropython,orionrobots/micropython,pfalcon/micropython,cloudformdesign/micropython,feilongfl/micropython,dmazzella/micropython,cnoviello/micropython,mpalomer/micropython,galenhz/micropython,lowRISC/micropython,kerneltask/micropython,mianos/micropython,warner83/micropython,bvernoux/micropython,deshipu/micropython,Timmenem/micropython,MrSurly/micropython,pfalcon/micropython,xhat/micropython,misterdanb/micropython,lbattraw/micropython,jimkmc/micropython,puuu/micropython,cnoviello/micropython,alex-march/micropython,matthewelse/micropython,noahchense/micropython,feilongfl/micropython,toolmacher/micropython,tobbad/micropython,blazewicz/micropython,misterdanb/micropython,tuc-osg/micropython,supergis/micropython,galenhz/micropython,PappaPeppar/micropython,ruffy91/micropython,hosaka/micropython,micropython/micropython-esp32,dinau/micropython,cwyark/micropython,dinau/micropython,adafruit/circuitpython,ryannathans/micropython,toolmacher/micropython,jmarcelino/pycom-micropython,HenrikSolver/micropython,kostyll/micropython,henriknelson/micropython,ahotam/micropython,cloudformdesign/micropython,noahwilliamsson/micropython,jmarcelino/pycom-micropython,jmarcelino/pycom-micropython,henriknelson/micropython,KISSMonX/micropython,Peetz0r/micropython-esp32,warner83/micropython,suda/micropython,KISSMonX/micropython,ruffy91/micropython,puuu/micropython,dhylands/micropython,alex-march/micropython,emfcamp/micropython,emfcamp/micropython,Peetz0r/micropython-esp32,oopy/micropython,tobbad/micropython,TDAbboud/micropython,adafruit/circuitpython,jlillest/micropython,adafruit/circuitpython,ganshun666/micropython,danicampora/micropython,cloudformdesign/micropython,lowRISC/micropython,torwag/micropython,blazewicz/micropython,slzatz/micropython,dhylands/micropython,firstval/micropython,alex-march/micropython,mhoffma/micropython,utopiaprince/micropython,emfcamp/micropython,ceramos/micropython,Timmenem/micropython,KISSMonX/micropython,tobbad/micropython,mgyenik/micropython,ChuckM/micropython,PappaPeppar/micropython,omtinez/micropython,MrSurly/micropython,alex-robbins/micropython,torwag/micropython,ryannathans/micropython,Peetz0r/micropython-esp32,praemdonck/micropython,MrSurly/micropython,vriera/micropython,alex-robbins/micropython,mpalomer/micropython,galenhz/micropython,TDAbboud/micropython,puuu/micropython,kerneltask/micropython,vriera/micropython,stonegithubs/micropython,orionrobots/micropython,dhylands/micropython,tuc-osg/micropython,MrSurly/micropython,martinribelotta/micropython,ryannathans/micropython,lbattraw/micropython,tdautc19841202/micropython,SungEun-Steve-Kim/test-mp,dxxb/micropython,swegener/micropython,stonegithubs/micropython,pozetroninc/micropython,pozetroninc/micropython,Vogtinator/micropython,chrisdearman/micropython,suda/micropython,adafruit/micropython,neilh10/micropython,paul-xxx/micropython,warner83/micropython,rubencabrera/micropython,paul-xxx/micropython,xyb/micropython,MrSurly/micropython,adafruit/circuitpython,skybird6672/micropython,ericsnowcurrently/micropython,drrk/micropython,mgyenik/micropython,rubencabrera/micropython,matthewelse/micropython,martinribelotta/micropython,cloudformdesign/micropython,MrSurly/micropython-esp32,chrisdearman/micropython,bvernoux/micropython,SHA2017-badge/micropython-esp32,drrk/micropython,hiway/micropython,vitiral/micropython,HenrikSolver/micropython,ernesto-g/micropython,mhoffma/micropython,MrSurly/micropython-esp32,noahwilliamsson/micropython,ruffy91/micropython,danicampora/micropython,galenhz/micropython,xhat/micropython,selste/micropython,adafruit/micropython,micropython/micropython-esp32,orionrobots/micropython,Vogtinator/micropython,AriZuu/micropython,chrisdearman/micropython,selste/micropython,ceramos/micropython,ceramos/micropython,feilongfl/micropython,blmorris/micropython,skybird6672/micropython,mianos/micropython,Timmenem/micropython,heisewangluo/micropython,galenhz/micropython,slzatz/micropython,omtinez/micropython,methoxid/micropystat,tobbad/micropython,Vogtinator/micropython,xuxiaoxin/micropython,kerneltask/micropython,ahotam/micropython,ChuckM/micropython,skybird6672/micropython,xyb/micropython,tuc-osg/micropython,ericsnowcurrently/micropython,torwag/micropython,heisewangluo/micropython,lbattraw/micropython,hiway/micropython,dhylands/micropython,SungEun-Steve-Kim/test-mp,blazewicz/micropython,micropython/micropython-esp32,hosaka/micropython,ernesto-g/micropython,infinnovation/micropython,trezor/micropython,pramasoul/micropython,SHA2017-badge/micropython-esp32,Timmenem/micropython,blazewicz/micropython,MrSurly/micropython-esp32,SungEun-Steve-Kim/test-mp,adafruit/micropython,bvernoux/micropython,neilh10/micropython,ChuckM/micropython,misterdanb/micropython,warner83/micropython,swegener/micropython,mianos/micropython,alex-march/micropython,praemdonck/micropython,ruffy91/micropython,toolmacher/micropython,jimkmc/micropython,matthewelse/micropython,ahotam/micropython,kerneltask/micropython,adamkh/micropython,emfcamp/micropython,bvernoux/micropython,SHA2017-badge/micropython-esp32,HenrikSolver/micropython,tuc-osg/micropython,utopiaprince/micropython,firstval/micropython,adafruit/circuitpython,ganshun666/micropython,noahwilliamsson/micropython,mianos/micropython,KISSMonX/micropython,SungEun-Steve-Kim/test-mp,Peetz0r/micropython-esp32,suda/micropython,trezor/micropython,infinnovation/micropython,firstval/micropython,dhylands/micropython,cwyark/micropython,heisewangluo/micropython,tralamazza/micropython,blazewicz/micropython,dxxb/micropython,xyb/micropython,lowRISC/micropython,PappaPeppar/micropython,suda/micropython,tralamazza/micropython,hosaka/micropython,vitiral/micropython,xhat/micropython,swegener/micropython,EcmaXp/micropython,ahotam/micropython,ryannathans/micropython,henriknelson/micropython,henriknelson/micropython,TDAbboud/micropython,AriZuu/micropython,omtinez/micropython,orionrobots/micropython,danicampora/micropython,matthewelse/micropython,aethaniel/micropython,trezor/micropython,drrk/micropython,micropython/micropython-esp32,lbattraw/micropython,praemdonck/micropython,ganshun666/micropython,pozetroninc/micropython,mpalomer/micropython,kostyll/micropython,mhoffma/micropython,neilh10/micropython,toolmacher/micropython,HenrikSolver/micropython,KISSMonX/micropython,kerneltask/micropython,SHA2017-badge/micropython-esp32,ceramos/micropython,HenrikSolver/micropython,neilh10/micropython,cnoviello/micropython,methoxid/micropystat,hiway/micropython,adamkh/micropython,jimkmc/micropython,selste/micropython,dinau/micropython,methoxid/micropystat,AriZuu/micropython,cwyark/micropython,adamkh/micropython,blmorris/micropython