patches to build on freebsd 12

- added cc and ar scripts for freebsd12.amd64
- fix for sfio macro SF_FLAGS also being defined for sendfile(2) in socket.h
-- fix is to hide the sendfile(2) macro
- defined _STDFILE_DECLARED to handle FILE macro incompatibility
- added test in std/features/procfs to deal with freebsd kvm interface
-- being different from what AST expects (for ps.c)
- fix for std/banner.c to clean up main() definition
- changed comment in ar.* scripts to match cc.* scripts

src/lib/libast/sfio/sfhdr.h

@@ -1305,4 +1305,9 @@ extern int	poll _ARG_((ulong, struct pollfd*, int));
 
 _END_EXTERNS_
 
+#ifdef _SF_HIDESFFLAGS
+#undef SF_FLAGS
+#define SF_FLAGS        0177177 /* PUBLIC FLAGS PASSABLE TO SFNEW()     */
+#endif
+
 #endif /*_SFHDR_H*/