[lsan] Allocator for standalone LSan.

This is the first in a series of CLs implementing LeakSanitizer.
http://clang.llvm.org/docs/LeakSanitizer.html

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@182245 91177308-0d34-0410-b5e6-96231b3b80d8
[lsan] Thread registry for standalone LSan.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@182246 91177308-0d34-0410-b5e6-96231b3b80d8