llvmc now supports Clang

Greetings everybody!

In my quest to attract more users to llvmc, I've added support for
compilation via the Clang front-end (previously, only llvm-gcc was
supported). This is enabled with the '-clang' switch; basically, you
can now just alias 'ccc' to 'llvmc -clang' and get the same


    Compile via Clang:
    $ llvmc -clang test.c

    Compile via llvm-gcc:
    $ llvmc test.c

    Emit LLVM bitcode:
    $ llvmc -clang -c -emit-llvm test.c

    Emit LLVM bitcode assembly:
    $ llvmc -clang -S -emit-llvm test.c

    Verbose mode (print out all executed commands):
    $ llvmc -v -clang test.c

I'll be happy to hear your feedback/feature requests/bugreports.