Add code to honor the match_not_bol and match_not_eol regex flats. Fixes PR#22651. Thanks to Jim Porter for the report and suggested fix.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@232733 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed