ARM: remove dead CodeGen functions.

These two are no longer being used by NEON codegen.
[asan] adding support of 32-bit address sanitizer for MIPS

Summary: The patch supports both the clang cross-compiler and native compiler

Patch by Kumar Sukhani <Kumar.Sukhani@imgtec.com>

Test Plan:
Kumar had the following asan test results when compiled on a MIPS board:

  Expected Passes    : 96
  Expected Failures  : 2
  Unsupported Tests  : 84
  Unexpected Passes  : 4
  Unexpected Failures: 19

The list of unexpected failures can be found in the review.

Reviewers: kcc, petarj, dsanders

Reviewed By: kcc

Subscribers: farazs, kcc, llvm-commits

Differential Revision: http://reviews.llvm.org/D4208
[mips] Use __clear_cache builtin instead of cacheflush() in Unix Memory::InvalidateInstructionCache()

MIPS64 Android bionic has removed cacheflush(). Use __clear_cache() instead for 32-bit and 64-bit MIPS

Patch by Duane Sand <Duane.Sand@imgtec.com>
[OPENMP] Additional checking for 'collapse' clause.
[mips] Added support for assembling sdbbp.

Summary:
This instruction is re-encoded in MIPS32r6/MIPS64r6 without changing the
restrictions. We hadn't implemented it for earlier ISA's so it has been added to those too.

Differential Revision: http://reviews.llvm.org/D4265