DebugInfo: Remove forced column-info workaround for inlined calls

This workaround was to provide unique call sites to ensure LLVM's inline
debug info handling would properly unique two calls to the same function
on the same line. Instead, this has now been fixed in LLVM (r226736) and
the workaround here can be removed.

Originally committed in r176895, but this isn't a straight revert due to
all the changes since then. I just searched for anything ForcedColumn*
related and removed them.

We could test this - but it didn't strike me as terribly valuable once
we're no longer adding this workaround everything just works as expected
& it's no longer a special case to test for.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@226738 91177308-0d34-0410-b5e6-96231b3b80d8