[PATCH] [ASan, LSan] Improve tracking of thread creation.

[Alexey Samsonov]

>>! In D6441#24, @earthdok wrote:
> BTW, I think the ThreadRegistry::CreateThread() call should be moved into AsanThread::Create(). This code is duplicated across 4 uses of AsanThread::Create(), and anyway most other ThreadRegistry access is done via AsanThread (including ThreadRegistry::FinishThread()).

I agree, that would be nice.

http://reviews.llvm.org/D6441