librustdoc/html: recognize slices not to nest A tags.
librustdoc/html: recognize slices not to nest A tags.

1. A slice of parametrized type, say
   BorrowedRef { ... Vector(Generic(T)) }, is rendered as
   "<a href='primitive.slice.html'>&amp;[T]</a>"
2. A slice of other types, say
   BorrowedRef { ... Vector(int) }, is rendered as
   "<a href='primitive.slice.html'>&amp;[</a>
    <a href='primitive.int.html'>int</a>
    <a href='primitive.slice.html'>]</a>"
3. Other cases, say BorrowedRef { ... int }, are
   rendered as same as before:
   "&<a href='primitive.int.html'>int</a>"

Relevant W3C specs:
- http://www.w3.org/TR/html401/struct/links.html#h-12.2.2
  12.2.2 Nested links are illegal
- http://www.w3.org/TR/html5/text-level-semantics.html#the-a-element
  states A tag must not enclose any "interactive contents"
  which include A tags themselves.

jashank/rust,ruud-v-a/rust,carols10cents/rust,0x73/rust,ebfull/rust,kwantam/rust,quornian/rust,miniupnp/rust,ebfull/rust,dinfuehr/rust,l0kod/rust,aepsil0n/rust,zachwick/rust,mdinger/rust,ruud-v-a/rust,richo/rust,cllns/rust,omasanori/rust,quornian/rust,aepsil0n/rust,miniupnp/rust,AerialX/rust-rt-minimal,andars/rust,0x73/rust,AerialX/rust,graydon/rust,aneeshusa/rust,pshc/rust,0x73/rust,AerialX/rust,TheNeikos/rust,zachwick/rust,victorvde/rust,hauleth/rust,barosl/rust,dinfuehr/rust,rohitjoshi/rust,zaeleus/rust,pshc/rust,pelmers/rust,mahkoh/rust,AerialX/rust-rt-minimal,kimroen/rust,zaeleus/rust,miniupnp/rust,nwin/rust,kimroen/rust,carols10cents/rust,emk/rust,mdinger/rust,XMPPwocky/rust,defuz/rust,emk/rust,jashank/rust,ejjeong/rust,andars/rust,pshc/rust,philyoon/rust,GBGamer/rust,defuz/rust,kimroen/rust,l0kod/rust,zachwick/rust,victorvde/rust,TheNeikos/rust,ebfull/rust,0x73/rust,zachwick/rust,cllns/rust,AerialX/rust,jroesch/rust,richo/rust,avdi/rust,graydon/rust,victorvde/rust,ruud-v-a/rust,TheNeikos/rust,andars/rust,barosl/rust,rprichard/rust,vhbit/rust,ruud-v-a/rust,victorvde/rust,zachwick/rust,ktossell/rust,ejjeong/rust,mihneadb/rust,defuz/rust,rohitjoshi/rust,dinfuehr/rust,AerialX/rust,omasanori/rust,krzysz00/rust,dwillmer/rust,sae-bom/rust,defuz/rust,zubron/rust,krzysz00/rust,krzysz00/rust,quornian/rust,reem/rust,ejjeong/rust,vhbit/rust,XMPPwocky/rust,KokaKiwi/rust,rprichard/rust,untitaker/rust,zaeleus/rust,aepsil0n/rust,kwantam/rust,zubron/rust,ktossell/rust,0x73/rust,ebfull/rust,aneeshusa/rust,hauleth/rust,dinfuehr/rust,quornian/rust,seanrivera/rust,quornian/rust,jroesch/rust,l0kod/rust,omasanori/rust,gifnksm/rust,miniupnp/rust,emk/rust,cllns/rust,jroesch/rust,jroesch/rust,dwillmer/rust,reem/rust,krzysz00/rust,aneeshusa/rust,omasanori/rust,GBGamer/rust,GBGamer/rust,zubron/rust,gifnksm/rust,kimroen/rust,jashank/rust,aneeshusa/rust,jashank/rust,mihneadb/rust,rohitjoshi/rust,sae-bom/rust,untitaker/rust,kwantam/rust,ebfull/rust,AerialX/rust,zaeleus/rust,sae-bom/rust,nwin/rust,mihneadb/rust,pshc/rust,dinfuehr/rust,vhbit/rust,seanrivera/rust,bombless/rust,untitaker/rust,mvdnes/rust,TheNeikos/rust,jashank/rust,carols10cents/rust,mihneadb/rust,ejjeong/rust,pelmers/rust,dwillmer/rust,XMPPwocky/rust,mihneadb/rust,hauleth/rust,ruud-v-a/rust,AerialX/rust-rt-minimal,rohitjoshi/rust,barosl/rust,andars/rust,robertg/rust,l0kod/rust,hauleth/rust,rohitjoshi/rust,richo/rust,jroesch/rust,0x73/rust,l0kod/rust,zaeleus/rust,dwillmer/rust,pshc/rust,sae-bom/rust,robertg/rust,emk/rust,KokaKiwi/rust,GBGamer/rust,gifnksm/rust,jroesch/rust,richo/rust,avdi/rust,omasanori/rust,AerialX/rust-rt-minimal,jashank/rust,ebfull/rust,KokaKiwi/rust,quornian/rust,avdi/rust,KokaKiwi/rust,ktossell/rust,avdi/rust,zachwick/rust,cllns/rust,nwin/rust,untitaker/rust,seanrivera/rust,robertg/rust,omasanori/rust,untitaker/rust,vhbit/rust,KokaKiwi/rust,GBGamer/rust,AerialX/rust-rt-minimal,mahkoh/rust,ktossell/rust,l0kod/rust,rohitjoshi/rust,dwillmer/rust,cllns/rust,barosl/rust,hauleth/rust,rprichard/rust,kwantam/rust,krzysz00/rust,kwantam/rust,vhbit/rust,bombless/rust,nwin/rust,vhbit/rust,rprichard/rust,sae-bom/rust,ktossell/rust,richo/rust,andars/rust,mvdnes/rust,zubron/rust,l0kod/rust,TheNeikos/rust,bombless/rust,dwillmer/rust,mahkoh/rust,mahkoh/rust,nwin/rust,quornian/rust,kimroen/rust,reem/rust,XMPPwocky/rust,mdinger/rust,ktossell/rust,avdi/rust,nwin/rust,gifnksm/rust,aidancully/rust,hauleth/rust,aidancully/rust,mahkoh/rust,bombless/rust,philyoon/rust,miniupnp/rust,mvdnes/rust,mdinger/rust,seanrivera/rust,avdi/rust,dwillmer/rust,graydon/rust,jashank/rust,seanrivera/rust,aepsil0n/rust,cllns/rust,carols10cents/rust,mdinger/rust,reem/rust,mahkoh/rust,aneeshusa/rust,dwillmer/rust,barosl/rust,barosl/rust,ruud-v-a/rust,aidancully/rust,barosl/rust,bombless/rust,zubron/rust,nwin/rust,miniupnp/rust,pelmers/rust,kwantam/rust,sae-bom/rust,robertg/rust,philyoon/rust,aepsil0n/rust,bombless/rust-docs-chinese,vhbit/rust,graydon/rust,aneeshusa/rust,andars/rust,pshc/rust,pelmers/rust,pelmers/rust,aidancully/rust,defuz/rust,miniupnp/rust,victorvde/rust,KokaKiwi/rust,mvdnes/rust,AerialX/rust,nwin/rust,XMPPwocky/rust,victorvde/rust,philyoon/rust,dinfuehr/rust,ejjeong/rust,aidancully/rust,zubron/rust,reem/rust,jroesch/rust,reem/rust,bombless/rust,pshc/rust,GBGamer/rust,ktossell/rust,philyoon/rust,kimroen/rust,gifnksm/rust,aepsil0n/rust,pelmers/rust,mvdnes/rust,zaeleus/rust,0x73/rust,untitaker/rust,philyoon/rust,GBGamer/rust,pshc/rust,emk/rust,robertg/rust,l0kod/rust,rprichard/rust,GBGamer/rust,jroesch/rust,XMPPwocky/rust,rprichard/rust,mvdnes/rust,richo/rust,zubron/rust,ejjeong/rust,emk/rust,carols10cents/rust,gifnksm/rust,graydon/rust,graydon/rust,mdinger/rust,defuz/rust,vhbit/rust,TheNeikos/rust,robertg/rust,miniupnp/rust,seanrivera/rust,jashank/rust,emk/rust,AerialX/rust-rt-minimal,carols10cents/rust,krzysz00/rust,kimroen/rust,aidancully/rust,zubron/rust,mihneadb/rust