auto merge of #9923 : thestinger/rust/managed_boxes, r=brson
auto merge of #9923 : thestinger/rust/managed_boxes, r=brson

I'll flip this on after doing a snapshot. This syntax may or may not
stay around, and managed boxes are currently not very useful. They have
the same overall performance characteristics as `std::rc::Rc`, but are
significantly slower, allocate larger boxes and hold onto the memory
beyond when it is needed due to lacking move semantics.

There are currently two useful aspects of the type:

* the dereference sugar, which we should implement for `Rc`
* the annihilator freeing cycles at the end of the task

untitaker/rust,quornian/rust,zaeleus/rust,ktossell/rust,ruud-v-a/rust,ejjeong/rust,TheNeikos/rust,pythonesque/rust,kwantam/rust,defuz/rust,hauleth/rust,ebfull/rust,bombless/rust,vhbit/rust,GBGamer/rust,jroesch/rust,miniupnp/rust,aturon/rust,barosl/rust,ebfull/rust,l0kod/rust,dwillmer/rust,servo/rust,michaelballantyne/rust-gpu,ejjeong/rust,aepsil0n/rust,KokaKiwi/rust,XMPPwocky/rust,seanrivera/rust,kwantam/rust,ktossell/rust,andars/rust,omasanori/rust,aturon/rust,victorvde/rust,servo/rust,SiegeLord/rust,seanrivera/rust,AerialX/rust-rt-minimal,barosl/rust,pshc/rust,pythonesque/rust,miniupnp/rust,P1start/rust,mihneadb/rust,emk/rust,SiegeLord/rust,sae-bom/rust,pythonesque/rust,nham/rust,mahkoh/rust,zaeleus/rust,TheNeikos/rust,nwin/rust,XMPPwocky/rust,jbclements/rust,hauleth/rust,michaelballantyne/rust-gpu,carols10cents/rust,aidancully/rust,AerialX/rust-rt-minimal,SiegeLord/rust,AerialX/rust,aidancully/rust,erickt/rust,pshc/rust,rohitjoshi/rust,jroesch/rust,stepancheg/rust-ide-rust,jroesch/rust,Ryman/rust,AerialX/rust-rt-minimal,bhickey/rand,quornian/rust,ejjeong/rust,vhbit/rust,hauleth/rust,krzysz00/rust,erickt/rust,pczarn/rust,nwin/rust,untitaker/rust,pshc/rust,reem/rust,rprichard/rust,miniupnp/rust,graydon/rust,pshc/rust,kimroen/rust,ebfull/rust,pelmers/rust,aneeshusa/rust,robertg/rust,pczarn/rust,stepancheg/rust-ide-rust,pythonesque/rust,philyoon/rust,SiegeLord/rust,pshc/rust,zachwick/rust,quornian/rust,quornian/rust,kimroen/rust,michaelballantyne/rust-gpu,seanrivera/rust,pelmers/rust,ejjeong/rust,sae-bom/rust,jashank/rust,l0kod/rust,philyoon/rust,krzysz00/rust,AerialX/rust,mahkoh/rust,kwantam/rust,graydon/rust,kimroen/rust,pczarn/rust,pczarn/rust,KokaKiwi/rust,robertg/rust,Ryman/rust,l0kod/rust,KokaKiwi/rust,bombless/rust,barosl/rust,XMPPwocky/rust,jroesch/rust,mdinger/rust,avdi/rust,defuz/rust,avdi/rust,sae-bom/rust,gifnksm/rust,mihneadb/rust,aepsil0n/rust,mitsuhiko/rust,0x73/rust,aidancully/rust,dwillmer/rust,fabricedesre/rust,dwillmer/rust,victorvde/rust,Ryman/rust,victorvde/rust,GBGamer/rust,jashank/rust,l0kod/rust,seanrivera/rust,waynenilsen/rand,andars/rust,pythonesque/rust,zubron/rust,andars/rust,defuz/rust,quornian/rust,aepsil0n/rust,mahkoh/rust,nham/rust,jbclements/rust,ebfull/rust,GBGamer/rust,hauleth/rust,mahkoh/rust,TheNeikos/rust,omasanori/rust,barosl/rust,gifnksm/rust,emk/rust,jbclements/rust,aepsil0n/rust,michaelballantyne/rust-gpu,miniupnp/rust,untitaker/rust,GBGamer/rust,barosl/rust,robertg/rust,nham/rust,ruud-v-a/rust,sae-bom/rust,mahkoh/rust,pelmers/rust,mitsuhiko/rust,kimroen/rust,Ryman/rust,rohitjoshi/rust,stepancheg/rust-ide-rust,defuz/rust,zubron/rust,miniupnp/rust,aturon/rust,nwin/rust,P1start/rust,TheNeikos/rust,dwillmer/rust,stepancheg/rust-ide-rust,aneeshusa/rust,richo/rust,0x73/rust,P1start/rust,robertg/rust,0x73/rust,GrahamDennis/rand,vhbit/rust,untitaker/rust,aepsil0n/rust,l0kod/rust,bombless/rust-docs-chinese,dinfuehr/rust,reem/rust,0x73/rust,gifnksm/rust,kimroen/rust,zubron/rust,barosl/rust,jbclements/rust,mitsuhiko/rust,jroesch/rust,fabricedesre/rust,zaeleus/rust,fabricedesre/rust,dinfuehr/rust,0x73/rust,philyoon/rust,zachwick/rust,bluss/rand,seanrivera/rust,stepancheg/rust-ide-rust,kimroen/rust,fabricedesre/rust,reem/rust,nwin/rust,mihneadb/rust,victorvde/rust,jashank/rust,l0kod/rust,servo/rust,pshc/rust,ebfull/rust,jbclements/rust,philyoon/rust,servo/rust,pythonesque/rust,TheNeikos/rust,mdinger/rust,reem/rust,michaelballantyne/rust-gpu,graydon/rust,P1start/rust,l0kod/rust,zachwick/rust,nwin/rust,michaelballantyne/rust-gpu,hauleth/rust,graydon/rust,zubron/rust,TheNeikos/rust,philyoon/rust,nham/rust,miniupnp/rust,carols10cents/rust,XMPPwocky/rust,jashank/rust,michaelballantyne/rust-gpu,victorvde/rust,mdinger/rust,seanrivera/rust,miniupnp/rust,cllns/rust,ktossell/rust,untitaker/rust,mdinger/rust,cllns/rust,carols10cents/rust,mdinger/rust,vhbit/rust,dwillmer/rust,andars/rust,erickt/rust,emk/rust,gifnksm/rust,robertg/rust,krzysz00/rust,vhbit/rust,ruud-v-a/rust,vhbit/rust,l0kod/rust,stepancheg/rust-ide-rust,nham/rust,achanda/rand,krzysz00/rust,pelmers/rust,nham/rust,aidancully/rust,pshc/rust,ebfull/rand,mvdnes/rust,richo/rust,bombless/rust,bombless/rust,pythonesque/rust,andars/rust,KokaKiwi/rust,pshc/rust,graydon/rust,mitsuhiko/rust,nwin/rust,sae-bom/rust,fabricedesre/rust,ktossell/rust,zubron/rust,dinfuehr/rust,cllns/rust,ejjeong/rust,ruud-v-a/rust,vhbit/rust,quornian/rust,avdi/rust,bombless/rust,P1start/rust,AerialX/rust,rprichard/rust,emk/rust,erickt/rust,omasanori/rust,quornian/rust,mihneadb/rust,aturon/rust,kwantam/rust,andars/rust,jroesch/rust,rohitjoshi/rust,rprichard/rust,jashank/rust,defuz/rust,omasanori/rust,ejjeong/rust,barosl/rust,zubron/rust,rohitjoshi/rust,jashank/rust,omasanori/rust,KokaKiwi/rust,SiegeLord/rust,jashank/rust,rprichard/rust,pczarn/rust,jroesch/rust,rohitjoshi/rust,aidancully/rust,avdi/rust,XMPPwocky/rust,cllns/rust,jashank/rust,servo/rust,reem/rust,zachwick/rust,aturon/rust,omasanori/rust,ktossell/rust,mahkoh/rust,jbclements/rust,mitsuhiko/rust,pczarn/rust,gifnksm/rust,AerialX/rust,retep998/rand,avdi/rust,krzysz00/rust,dinfuehr/rust,aneeshusa/rust,ktossell/rust,Ryman/rust,carols10cents/rust,graydon/rust,kimroen/rust,ebfull/rust,nham/rust,hauleth/rust,fabricedesre/rust,cllns/rust,richo/rust,philyoon/rust,Ryman/rust,kwantam/rust,rprichard/rust,zaeleus/rust,erickt/rust,P1start/rust,nwin/rust,vhbit/rust,pelmers/rust,richo/rust,mdinger/rust,AerialX/rust,pelmers/rust,jbclements/rust,rprichard/rust,aneeshusa/rust,ruud-v-a/rust,SiegeLord/rust,mihneadb/rust,aepsil0n/rust,ktossell/rust,defuz/rust,emk/rust,mihneadb/rust,sae-bom/rust,carols10cents/rust,zaeleus/rust,gifnksm/rust,mvdnes/rust,cllns/rust,avdi/rust,aneeshusa/rust,AerialX/rust-rt-minimal,GBGamer/rust,fabricedesre/rust,erickt/rust,jbclements/rust,AerialX/rust-rt-minimal,AerialX/rust,dwillmer/rust,aneeshusa/rust,KokaKiwi/rust,aturon/rust,mvdnes/rust,huonw/rand,stepancheg/rust-ide-rust,victorvde/rust,aidancully/rust,zubron/rust,GBGamer/rust,shepmaster/rand,mitsuhiko/rust,emk/rust,0x73/rust,jbclements/rust,zachwick/rust,nwin/rust,zubron/rust,robertg/rust,kwantam/rust,mvdnes/rust,XMPPwocky/rust,aturon/rust,arthurprs/rand,jroesch/rust,untitaker/rust,reem/rust,richo/rust,carols10cents/rust,rohitjoshi/rust,GBGamer/rust,0x73/rust,zachwick/rust,dinfuehr/rust,mitsuhiko/rust,P1start/rust,dinfuehr/rust,GBGamer/rust,dwillmer/rust,SiegeLord/rust,miniupnp/rust,dwillmer/rust,richo/rust,Ryman/rust,AerialX/rust-rt-minimal,erickt/rust,servo/rust,krzysz00/rust,servo/rust,mvdnes/rust,mvdnes/rust,pczarn/rust,emk/rust,bombless/rust,zaeleus/rust,ruud-v-a/rust