SanitizerCommon: 64-bit SPARC/Linux port

Summary:
This patch contains the bits required to make the common 32-bit allocator work on SPARC64/Linux.

Patch by Eric Botcazou.

Reviewers: #sanitizers, vitalybuka

Reviewed By: #sanitizers, vitalybuka

Subscribers: krytarowski, vitalybuka, ro, jyknight, kubamracek, fedor.sergeev, jdoerfert, llvm-commits, #sanitizers

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D58432

llvm-svn: 355978