N3644 support for vector<bool>

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@187910 91177308-0d34-0410-b5e6-96231b3b80d8
N3644 support for vector<bool>

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@187911 91177308-0d34-0410-b5e6-96231b3b80d8