Tag build swift-DEVELOPMENT-SNAPSHOT-2016-08-18-a
Merge remote-tracking branch 'origin/swift-3.0-branch' into stable

* origin/swift-3.0-branch:
  Fixup for the cherrypick of 4b0d2c12 (r277458) into clang-800. The lit test used "nullptr", which clang-800 complains about, so let's just use NULL instead.
  Follow-up for r277458: Update the tsan_mman_test.cc unit test.
  [tsan] Fix behavior of realloc(nullptr, 0) on Darwin