Merge branch 'master' of http://llvm.org/git/libcxx
EricQWF's code coverage work showed that none of the libc++ tests were exercising some code in vector<bool>. Add more tests in an attempt to get better coverage

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@221644 91177308-0d34-0410-b5e6-96231b3b80d8
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'origin/master'