auto merge of #19514 : jbranchaud/rust/add-btree-set-bitor, r=Gankro
auto merge of #19514 : jbranchaud/rust/add-btree-set-bitor, r=Gankro

I am trying to add an implementation of `bitor` for `BTreeSet`. I think I am most of the way there, but I am going to need some guidance to take it all the way.

When I run `make check`, I get:

```
error: cannot move out of dereference of `&`-pointer
self.union(_rhs).map(|&i| i).collect::<BTreeSet<T>>()
                      ^~
```

I'd appreciate any nudges in the right direction. If I can figure this one out, I am sure I will be able to implement `bitand`, `bitxor`, and `sub` as well.

/cc @Gankro 

---

**Update**

I have added implementations for `BitOr`, `BitAnd`, `BitXor`, and `Sub` for `BTreeSet`.

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