Improve the accuracy of the inlining heuristic looking for the

Improve the accuracy of the inlining heuristic looking for the
case where a static caller is itself inlined everywhere else, and
thus may go away if it doesn't get too big due to inlining other
things into it.  If there are references to the caller other than
calls, it will not be removed; account for this.
This results in same-day completion of the case in PR8853.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122821 91177308-0d34-0410-b5e6-96231b3b80d8