std::borrow: Use raw pointer comparison for `ref_eq`

Compare as `*T` in `ref_eq` instead of casting to uint, to match what
std::ptr does.
Remove and replace cond! Closes #9282.
auto merge of #9291 : jzelinskie/rust/remove-cond, r=alexcrichton

This is my first contribution, so please point out anything that I may have missed.

I consulted IRC and settled on `match () { ... }` for most of the replacements.
auto merge of #9292 : blake2-ppc/rust/borrow-ref-eq, r=huonw

std::borrow: Use raw pointer comparison for `ref_eq`

Compare as `*T` in `ref_eq` instead of casting to uint, to match what
std::ptr does.
Turned extra::getopts functions into methods
Some minor api and doc adjustments
auto merge of #9267 : Kimundi/rust/master, r=huonw