Stability: tweak rules for trait impls
Stability: tweak rules for trait impls

There is currently no way to specify the stability level for a trait
impl produced by `deriving`. This patch is a stopgap solution that:

* Turns of stability inheritance for trait impls, and
* Uses the stability level of the *trait* if no level is directly
  specified.

That is, manual trait impls may still provide a directly stability
level, but `deriving` will use the level of the trait. While not a
perfect solution, it should be good enough for 1.0 API stabilization, as
we will like *remove* any unwanted impls outright.

graydon/rust,mdinger/rust,hauleth/rust,rohitjoshi/rust,krzysz00/rust,mihneadb/rust,pshc/rust,ebfull/rust,mvdnes/rust,AerialX/rust,avdi/rust,avdi/rust,AerialX/rust-rt-minimal,l0kod/rust,mihneadb/rust,defuz/rust,sae-bom/rust,ejjeong/rust,nwin/rust,TheNeikos/rust,robertg/rust,jashank/rust,jashank/rust,untitaker/rust,jroesch/rust,XMPPwocky/rust,vhbit/rust,rohitjoshi/rust,rprichard/rust,kwantam/rust,ktossell/rust,zaeleus/rust,miniupnp/rust,richo/rust,kwantam/rust,XMPPwocky/rust,zubron/rust,victorvde/rust,AerialX/rust-rt-minimal,omasanori/rust,avdi/rust,jashank/rust,jashank/rust,ejjeong/rust,ebfull/rust,andars/rust,pshc/rust,aneeshusa/rust,AerialX/rust-rt-minimal,kimroen/rust,AerialX/rust-rt-minimal,sae-bom/rust,aneeshusa/rust,ebfull/rust,reem/rust,dinfuehr/rust,dwillmer/rust,zachwick/rust,philyoon/rust,victorvde/rust,defuz/rust,KokaKiwi/rust,kimroen/rust,mdinger/rust,TheNeikos/rust,aidancully/rust,nwin/rust,graydon/rust,zaeleus/rust,sae-bom/rust,krzysz00/rust,bombless/rust,robertg/rust,l0kod/rust,avdi/rust,aneeshusa/rust,aneeshusa/rust,carols10cents/rust,cllns/rust,dinfuehr/rust,ejjeong/rust,ktossell/rust,aidancully/rust,nwin/rust,reem/rust,carols10cents/rust,jroesch/rust,mahkoh/rust,rprichard/rust,jroesch/rust,philyoon/rust,reem/rust,jashank/rust,zaeleus/rust,rprichard/rust,GBGamer/rust,ktossell/rust,rohitjoshi/rust,gifnksm/rust,krzysz00/rust,aepsil0n/rust,nwin/rust,mdinger/rust,dwillmer/rust,ruud-v-a/rust,robertg/rust,ktossell/rust,zachwick/rust,mdinger/rust,zaeleus/rust,untitaker/rust,reem/rust,zaeleus/rust,aepsil0n/rust,mahkoh/rust,hauleth/rust,philyoon/rust,zubron/rust,hauleth/rust,dwillmer/rust,kimroen/rust,seanrivera/rust,andars/rust,ebfull/rust,aepsil0n/rust,jashank/rust,andars/rust,kimroen/rust,jroesch/rust,nwin/rust,zachwick/rust,vhbit/rust,nwin/rust,bombless/rust,kwantam/rust,rohitjoshi/rust,vhbit/rust,pshc/rust,omasanori/rust,l0kod/rust,dwillmer/rust,miniupnp/rust,dwillmer/rust,GBGamer/rust,aepsil0n/rust,jroesch/rust,GBGamer/rust,pshc/rust,untitaker/rust,jashank/rust,hauleth/rust,sae-bom/rust,philyoon/rust,aneeshusa/rust,zaeleus/rust,andars/rust,kimroen/rust,graydon/rust,victorvde/rust,defuz/rust,omasanori/rust,bombless/rust,vhbit/rust,mvdnes/rust,mahkoh/rust,AerialX/rust,mihneadb/rust,pshc/rust,graydon/rust,ruud-v-a/rust,kwantam/rust,nwin/rust,dinfuehr/rust,miniupnp/rust,aidancully/rust,robertg/rust,avdi/rust,richo/rust,AerialX/rust,avdi/rust,seanrivera/rust,cllns/rust,hauleth/rust,reem/rust,dinfuehr/rust,pelmers/rust,ruud-v-a/rust,omasanori/rust,gifnksm/rust,mihneadb/rust,l0kod/rust,KokaKiwi/rust,AerialX/rust-rt-minimal,AerialX/rust,bombless/rust,l0kod/rust,defuz/rust,pelmers/rust,miniupnp/rust,TheNeikos/rust,zachwick/rust,richo/rust,dinfuehr/rust,dinfuehr/rust,hauleth/rust,vhbit/rust,rprichard/rust,graydon/rust,gifnksm/rust,pelmers/rust,jroesch/rust,mdinger/rust,sae-bom/rust,kwantam/rust,rohitjoshi/rust,cllns/rust,mvdnes/rust,ebfull/rust,robertg/rust,bombless/rust,gifnksm/rust,TheNeikos/rust,ebfull/rust,GBGamer/rust,seanrivera/rust,carols10cents/rust,pelmers/rust,untitaker/rust,sae-bom/rust,l0kod/rust,ejjeong/rust,mdinger/rust,bombless/rust,aidancully/rust,l0kod/rust,nwin/rust,miniupnp/rust,andars/rust,philyoon/rust,zubron/rust,KokaKiwi/rust,miniupnp/rust,andars/rust,seanrivera/rust,zubron/rust,vhbit/rust,krzysz00/rust,seanrivera/rust,kimroen/rust,mvdnes/rust,rprichard/rust,XMPPwocky/rust,untitaker/rust,rprichard/rust,jashank/rust,pshc/rust,KokaKiwi/rust,KokaKiwi/rust,pshc/rust,reem/rust,dwillmer/rust,pshc/rust,victorvde/rust,untitaker/rust,jroesch/rust,pelmers/rust,aidancully/rust,AerialX/rust-rt-minimal,bombless/rust-docs-chinese,cllns/rust,mihneadb/rust,graydon/rust,aepsil0n/rust,mahkoh/rust,omasanori/rust,kimroen/rust,l0kod/rust,ruud-v-a/rust,kwantam/rust,robertg/rust,ktossell/rust,XMPPwocky/rust,ktossell/rust,omasanori/rust,aepsil0n/rust,carols10cents/rust,AerialX/rust,ktossell/rust,KokaKiwi/rust,zachwick/rust,GBGamer/rust,zachwick/rust,vhbit/rust,XMPPwocky/rust,aneeshusa/rust,dwillmer/rust,mvdnes/rust,richo/rust,rohitjoshi/rust,XMPPwocky/rust,seanrivera/rust,victorvde/rust,aidancully/rust,vhbit/rust,TheNeikos/rust,philyoon/rust,dwillmer/rust,victorvde/rust,zubron/rust,mvdnes/rust,gifnksm/rust,ejjeong/rust,zubron/rust,defuz/rust,carols10cents/rust,cllns/rust,miniupnp/rust,mahkoh/rust,zubron/rust,GBGamer/rust,zubron/rust,ruud-v-a/rust,TheNeikos/rust,ejjeong/rust,richo/rust,mahkoh/rust,richo/rust,GBGamer/rust,ruud-v-a/rust,AerialX/rust,gifnksm/rust,pelmers/rust,krzysz00/rust,krzysz00/rust,GBGamer/rust,miniupnp/rust,carols10cents/rust,mihneadb/rust,cllns/rust,defuz/rust,jroesch/rust