Revert "Rework fix for PR19460 - Use explicit bool as an extension instead."

This reverts commit 3a1b90a866b6d5d62a5f37fbfb3a1ee36cc70dd1.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@291921 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed