Revert r158700 and dependent patches r158716, r158717, and r158731.

The original r158700 caused crashes in the gcc test suite,
g++.abi/vtable3a.C among others. It also caused failures in the libc++
test suite.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@158749 91177308-0d34-0410-b5e6-96231b3b80d8
21 files changed