Try to speed up the slowest parts of the CommandLine library

- Replace std::map<std::string with StringMap
- Eliminate unnecessary std::string copies
- ~10% speed-up for clang's testsuite on my machine (debug build)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82312 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed