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.

Need this to correctly determine sysroot in rustc

Revert "stdlib: Migrate rust_file_is_dir() over to the C stack, and add a void type" due to build bustage on Windows

This reverts commit 9698ef89.

rustc: Allow calling native functions on the C stack that take generic arguments. They get turned into i8 pointers.

This reverts commit 6e56ec00.

This reverts commit 6e652588.

This reverts commit 007ec666.

Issue #667

It wasn't safe (computing the rval might invalidate the lval addr), and needlessly
complicating things (code was already building up intermediary results to work
around other unsafeties).

Issue #667

Issue #667

The retptr passed to a function will now often be the actual
destination of the returned value (as in `{field1: func1()}`).