Reimplement Thread Static Data MSan routines with TLS

Summary:
Thread Static Data cannot be used in early init on NetBSD
and FreeBSD. Reuse the MSan TSD API for compatibility with
existing code with an alternative implementation using Thread
Local Storage.

New version uses Thread Local Storage to store a pointer
with thread specific data. The destructor from TSD has been
replaced with a TLS destrucutor that is called upon thread
exit.

Reviewers: joerg, vitalybuka, jfb

Reviewed By: vitalybuka

Subscribers: emaste, jfb, llvm-commits, #sanitizers, mgorny

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D55703

llvm-svn: 350102