Adding mbed_trace to ppp_lwip
Adding mbed_trace to ppp_lwip

We introduce here mbed_trace to ppp_lwip shim layer.
If for some reason, FEATURE_COMMON_PAL is not included in the build,
dummies for trace functions are provided.

NXPmicro/mbed,adamgreen/mbed,YarivCol/mbed-os,pradeep-gr/mbed-os5-onsemi,pradeep-gr/mbed-os5-onsemi,pradeep-gr/mbed-os5-onsemi,mazimkhan/mbed-os,svogl/mbed-os,screamerbg/mbed,ryankurte/mbed-os,infinnovation/mbed-os,mmorenobarm/mbed-os,fahhem/mbed-os,mbedmicro/mbed,pradeep-gr/mbed-os5-onsemi,NXPmicro/mbed,fahhem/mbed-os,andcor02/mbed-os,mmorenobarm/mbed-os,c1728p9/mbed-os,andcor02/mbed-os,bcostm/mbed-os,NXPmicro/mbed,infinnovation/mbed-os,c1728p9/mbed-os,bcostm/mbed-os,kjbracey-arm/mbed,kjbracey-arm/mbed,bcostm/mbed-os,mikaleppanen/mbed-os,CalSol/mbed,monkiineko/mbed-os,CalSol/mbed,infinnovation/mbed-os,svogl/mbed-os,YarivCol/mbed-os,HeadsUpDisplayInc/mbed,andcor02/mbed-os,bcostm/mbed-os,nRFMesh/mbed-os,Archcady/mbed-os,HeadsUpDisplayInc/mbed,nRFMesh/mbed-os,karsev/mbed-os,mmorenobarm/mbed-os,Archcady/mbed-os,bcostm/mbed-os,ryankurte/mbed-os,monkiineko/mbed-os,adamgreen/mbed,mazimkhan/mbed-os,ryankurte/mbed-os,Archcady/mbed-os,nRFMesh/mbed-os,Archcady/mbed-os,betzw/mbed-os,pradeep-gr/mbed-os5-onsemi,adamgreen/mbed,catiedev/mbed-os,infinnovation/mbed-os,betzw/mbed-os,Archcady/mbed-os,karsev/mbed-os,adamgreen/mbed,mazimkhan/mbed-os,screamerbg/mbed,mmorenobarm/mbed-os,andcor02/mbed-os,karsev/mbed-os,bcostm/mbed-os,monkiineko/mbed-os,svogl/mbed-os,mazimkhan/mbed-os,HeadsUpDisplayInc/mbed,fahhem/mbed-os,fahhem/mbed-os,kjbracey-arm/mbed,mikaleppanen/mbed-os,andcor02/mbed-os,c1728p9/mbed-os,catiedev/mbed-os,fahhem/mbed-os,NXPmicro/mbed,c1728p9/mbed-os,c1728p9/mbed-os,monkiineko/mbed-os,mmorenobarm/mbed-os,CalSol/mbed,svogl/mbed-os,YarivCol/mbed-os,c1728p9/mbed-os,betzw/mbed-os,nRFMesh/mbed-os,svogl/mbed-os,mbedmicro/mbed,infinnovation/mbed-os,HeadsUpDisplayInc/mbed,betzw/mbed-os,pradeep-gr/mbed-os5-onsemi,betzw/mbed-os,mikaleppanen/mbed-os,nRFMesh/mbed-os,mazimkhan/mbed-os,YarivCol/mbed-os,monkiineko/mbed-os,catiedev/mbed-os,mbedmicro/mbed,HeadsUpDisplayInc/mbed,catiedev/mbed-os,CalSol/mbed,CalSol/mbed,HeadsUpDisplayInc/mbed,ryankurte/mbed-os,screamerbg/mbed,adamgreen/mbed,screamerbg/mbed,NXPmicro/mbed,kjbracey-arm/mbed,karsev/mbed-os,ryankurte/mbed-os,adamgreen/mbed,screamerbg/mbed,infinnovation/mbed-os,screamerbg/mbed,betzw/mbed-os,YarivCol/mbed-os,nRFMesh/mbed-os,svogl/mbed-os,monkiineko/mbed-os,mikaleppanen/mbed-os,mmorenobarm/mbed-os,Archcady/mbed-os,mazimkhan/mbed-os,catiedev/mbed-os,NXPmicro/mbed,ryankurte/mbed-os,mikaleppanen/mbed-os,karsev/mbed-os,mbedmicro/mbed,mbedmicro/mbed,karsev/mbed-os,fahhem/mbed-os,andcor02/mbed-os,catiedev/mbed-os,mikaleppanen/mbed-os,YarivCol/mbed-os,CalSol/mbed