Revert "Update for LLVM change (StringSaver)"

This reverts commit r215785 / 170ebf4f19459ae51a9561d0e65c87ee4c9b2c97.

LLD has some StringSavers that need to be updated. One of which takes a
lock and I need to investigate that more closely.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@215791 91177308-0d34-0410-b5e6-96231b3b80d8