Revision 289661 introduced the function DILocation::getMergedLocation for
merging of debug locations. At the time is was simply a stub which always
returned no location. This patch modifies getMergedLocation to handle the
case where the two locations are the same or can't be discriminated.
Differential Revision: https://reviews.llvm.org/D28521
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291809 91177308-0d34-0410-b5e6-96231b3b80d8