[CodeGen] Add to emitted DebugLoc information about coverage when it's required

Summary:
Some lines have a hit counter where they should not have one.
Cleanup stuff is located to the last line of the body which is most of the time a '}'.
And Exception stuff is added at the beginning of a function and at the end (represented by '{' and '}').
So in such cases, the DebugLoc used in GCOVProfiling.cpp must be marked as not covered.
This patch is a followup of https://reviews.llvm.org/D49915.
Tests in projects/compiler_rt are fixed by: https://reviews.llvm.org/D49917

Reviewers: marco-c, davidxl

Reviewed By: marco-c

Subscribers: dblaikie, cfe-commits, sylvestre.ledru

Differential Revision: https://reviews.llvm.org/D49916

llvm-svn: 342717