Make clang emit linkage names in debug info for subprograms when coverage info
is enabled. Also add a new -test-coverage cc1 flag which makes testing coverage
possible and add our first clang-side coverage test.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177470 91177308-0d34-0410-b5e6-96231b3b80d8