[sanitizer_common] Fuchsia OS support code

Submitted on behalf of Roland McGrath.

Reviewers: vitalybuka, alekseyshl, kcc

Reviewed By: vitalybuka

Subscribers: cryptoad, srhines, kubamracek, mgorny, phosek, filcab, llvm-commits

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D36031

llvm-svn: 309756