- Cache used characters in a bitset to reduce memory overhead to just 32 bytes.
- On my core2 this code is faster except when the checked string was very short
(smaller than the list of delimiters).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111817 91177308-0d34-0410-b5e6-96231b3b80d8