Audit cal(1)

1) Update manpage with the num-syntax.
2) Use size_t for years and derivatives.
3) Use putchar instead of printf wherever possible.
4) Update usage().
5) Style changes.

README

@@ -10,7 +10,7 @@ The following tools are implemented ('*' == finished, '#' == UTF-8 support,
     UTILITY         POSIX 2008 COMPLIANT         MISSING OPTIONS
     -------         --------------------         ---------------
 =*| basename        yes                          none
-=*  cal             yes                          none
+=*| cal             yes                          none
 =*| cat             yes                          none
 =*  chgrp           yes                          none
 =*| chmod           yes                          none