[msan] Fix origin_history_per_stack_limit=0 behavior.

It disables the per-stack limit.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@217030 91177308-0d34-0410-b5e6-96231b3b80d8
tsan: handle early signals
The second part of the fix of
https://code.google.com/p/thread-sanitizer/issues/detail?id=71



git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@217031 91177308-0d34-0410-b5e6-96231b3b80d8