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

Cast isdigit()'s argument to unsigned char.

ok guenther@

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@

Match bwrite()'s prototype with write()'s, zapping a lint comment
Delete casts to char* of arguments to bwrite() and free()

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.

2451 lines of strdup/sprintf/strcpy whacking. mostly ok'd by pjanzen
already, but he may have later changes to make still.

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@

Nothing but comments after #endif and #else; heko@iki.fi

$OpenBSD$

comment grammar

r?index -> strr?chr

branches: 1.1.1;
Initial revision