Update for nightly

I'm a bit shaky on the profile.rs changes (`thread_local!` and `RefCell`
relplacing `local_data_key!`), do make sure I haven't royally screwed
something up there.

Note that I haven't sucessfully run the various test_cargo_cross_compile
tests as I don't have an i686-unknown-linux-gnu rustc sitting around.
auto merge of #1003 : jmesmon/cargo/update-for-nightly, r=alexcrichton

I'm a bit shaky on the profile.rs changes (`thread_local!` and `RefCell` relplacing `local_data_key!`), do make sure I haven't royally screwed something up there.