Move asan-coverage into a separate phase.

Summary:
This change moves asan-coverage instrumentation
into a separate Module pass.
The other part of the change in clang introduces a new flag
-fsanitize-coverage=N.
Another small patch will update tests in compiler-rt.

With this patch no functionality change is expected except for the flag name.
The following changes will make the coverage instrumentation work with tsan/msan

Test Plan: Run regression tests, chromium.

Reviewers: nlewycky, samsonov

Reviewed By: nlewycky, samsonov

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D6152

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221718 91177308-0d34-0410-b5e6-96231b3b80d8
[Reassociate] Canonicalize negative constants out of expressions.

This is a reapplication of r221171, but we only perform the transformation
on expressions which include a multiplication.  We do not transform rem/div
operations as this doesn't appear to be safe in all cases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221721 91177308-0d34-0410-b5e6-96231b3b80d8
[asan] adding ShadowOffset64 for mips64, patch by Kumar Sukhani

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221725 91177308-0d34-0410-b5e6-96231b3b80d8
libLTO: Allow LTOCodeGenerator to own a context

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221726 91177308-0d34-0410-b5e6-96231b3b80d8
libLTO: Allow LTOModule to own a context

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221728 91177308-0d34-0410-b5e6-96231b3b80d8