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

include/llvm/Transforms/Instrumentation.h

@@ -78,6 +78,9 @@ ModulePass *createDataFlowSanitizerPass(StringRef ABIListFile = StringRef(),
                                         void *(*getArgTLS)() = nullptr,
                                         void *(*getRetValTLS)() = nullptr);
 
+// Insert SanitizerCoverage instrumentation.
+ModulePass *createSanitizerCoverageModulePass(int CoverageLevel);
+
 #if defined(__GNUC__) && defined(__linux__) && !defined(ANDROID)
 inline ModulePass *createDataFlowSanitizerPassForJIT(StringRef ABIListFile =
                                                          StringRef()) {