Implement Show for &mut [T]
native: Unlink unix socket paths on drop

This prevents unix sockets from remaining on the system all over the place, and
more closely mirrors the behavior of libuv and windows pipes.
There are no 64-bit Windows snapshots yet, so we'll use 32-bit ones instead.
Upgrade compiler-rt
add volatile copy/copy_nonoverlapping/set

This exposes volatile versions of the memset/memmove/memcpy intrinsics.

The volatile parameter must be constant, so this can't simply be a
parameter to our intrinsics.
Fixed Win64 build
auto merge of #13687 : exscape/mut-vector-Show/master, r=alexcrichton

Removes the need for hacks to println! mutable slices, among other things.
auto merge of #13690 : alexcrichton/rust/unlink-unix-pipe, r=brson

This prevents unix sockets from remaining on the system all over the place, and
more closely mirrors the behavior of libuv and windows pipes.
auto merge of #13692 : vadimcn/rust/Win64-pre, r=alexcrichton

Stack unwinding doesn't work yet, so this won't pass a lot of tests.
auto merge of #13693 : thestinger/rust/mem, r=alexcrichton

This exposes volatile versions of the memset/memmove/memcpy intrinsics.

The volatile parameter must be constant, so this can't simply be a
parameter to our intrinsics.