Add support to command line options:
* "-Dopts": the users can pass defined macros to the cc0 now
* "-Idirs": the sysroot is set to "." by default now
  -- the users can use "<stdio.h>" style #include in the c0 src code
     with the "-I/path/to/libi0" option added to cc0.
when cc0 compilation succeeds, it prints nothing with $? = 0; when -g defined, verbose msges are printed out to STDOUT; when error happens, the error msges are printed out with $? != 0