Use a more idiomatic way to disable debug locations.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@180931 91177308-0d34-0410-b5e6-96231b3b80d8
Ensure that the line table for functions with cleanups is sequential.

If there is cleanup code, the cleanup code gets the debug location of
the closing '}'. The subsequent ret IR-instruction does not get a
debug location. The return _expression_ will get the debug location
of the return statement.

If the function contains only a single, simple return statement,
the cleanup code may become the first breakpoint in the function.
In this case we set the debug location for the cleanup code
to the location of the return statement.

rdar://problem/13442648

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@180932 91177308-0d34-0410-b5e6-96231b3b80d8