Remove several casts to (char *) 0 and replace them by NULL

Prompted and OK by tb@

This diff is rather large, but it's just simply removing unnecessary headers
, remove some lint-style comments, add missing void to functions without args,
also some function prototypes (extern) were missing their args, so I added them
as they were defined in hack.h

OK tb@ on separate diffs

Annotate funcs with __attribute__((printf(...))) and clean up the fallout:
* lots of foo(str) --> foo("%s", str) transformations
* one totally insane foo(fmt, ap) --> vfoo(fmt, ap) conversion: how did
this ever work?
* prefer const char[] over char* for static format strings, as it lets
gcc check the format and eliminates an unnecessary pointer

ok beck@

rcsid[] and sccsid[] and copyright[] are essentially unmaintained (and
unmaintainable). these days, people use source. these id's do not provide
any benefit, and do hurt the small install media
(the 33,000 line diff is essentially mechanical)
ok with the idea millert, ok dms

De-register, ANSIfy, clean up.

hack is free

Thanks to Andries Brouwer, Jay Fenlason and the folks at CWI for their
efforts.

http://www.cwi.nl/~aeb/games/hack/hack.html

ok deraadt@

$OpenBSD$

branches: 1.1.1;
Initial revision