Support OSX. Close #4.

  * libtcc does not provide a way to determine errors and warnings.
    * Then, string based determination and use carp() if it's not fatal
      error.
    * Because OSX header file used `#warnings`.
  * Added workaround typedef code for OSX.
    * See http://comments.gmane.org/gmane.comp.compilers.tinycc.devel/325
Use return value of tcc_compile_string() to determine errors and
warnings.
Suggested by @run4flat.
Merge pull request #5 from tsee/osx

Support OSX. Close #4.

Looks good to me as well, thank you!