This reverts commit 100e0264.

Issue #1008

Closes #1005

rt: Make C stack switching Valgrind-clean by warning Valgrind when we're about to write to the C stack from the Rust stack

Somehow these started showing up on the tinderbox

We don't currently rpath native libs, but we do know where rustrt is
located and everything needs to link to it.

Setting it to the host libs uses those compiled from the previous stage

It was causing OS X Lion to hang and (according to Apple) is undefined
in any case

The stage0 compiler can't be fixed anyway. We used to have this in place but I
lost it during recent build changes.

Closes #667

Call trans_temp_lval if you want the old fallback-to-temporary behaviour.

Issue #667

Issue #667

It's not needed.

Issue #667

This reverts commit 11e407aa.

This reverts commit ce9e0fc9.

This reverts commit 276dfc61.