std: Remove ThreadPerCore spawn mode. Unused
std::rt: Rename RUST_TEST_THREADS to RUST_RT_TEST_THREADS
rt: Diagnose bad alloc index in release_alloc with RUSTRT_TRACK_ALLOCATIONS
rt: Print alloc backtraces for bad release_alloc with RUSTRT_TRACK_ALLOCATIONS

Probably the env var should be renamed from DETAILED_LEAKS but I'm leaving
aside that breaking change for now.
testsuite: Add compile-fail test for #5883
testsuite: Test for #6153, closes #6153
Fix warnings in libextra tests

Most of these are "unneccesary allocation" in bitv, for ~[false, ..] instead
of [false, ..].
Fix warnings in libstd and librusti tests
remove non-portable sed invocation as brson says we no longer have clang in tree.
librustc: Remove a bunch of `@` boxes from `Match`.

This will be needed to add `'static` bounds to `@`.
auto merge of #7854 : brson/rust/rt-test-threads, r=pcwalton
auto merge of #7856 : brson/rust/no-thread-per-core, r=pcwalton

This doesn't make sense under the new scheduler.
auto merge of #7857 : blake2-ppc/rust/fix-test-warnings, r=alexcrichton

Fix warnings that only show up when compiling the tests for libstd, libextra and one in librusti. Only trivial changes.
auto merge of #7859 : kmcallister/rust/rt-diag-messages, r=pcwalton

I added these while tracking down heap corruption in Servo.
auto merge of #7863 : catamorphism/rust/issue-5883, r=catamorphism
auto merge of #7868 : pnkfelix/rust/issue6929-remove-bogus-sed-invoke-from-configure, r=brson

... in tree.

Fix #6929
auto merge of #7871 : pcwalton/rust/de-at-match, r=brson

This will be needed to add `'static` bounds to `@`.

r? @nikomatsakis