bug fix for 1.0.2 uptodate routine...

[Jeff Myers]

A previous fix for version 1.0.1 in the file hack.stat.c can be applied
to version 1.0.2 hack.unix.c.  The diff follows for using mtime rather than
ctime in checking if a saved level or game is out of date.

Just lost a saved game due to this; arg!!!!!  Somebody apparently tried to
hard link to the game, modifying the ctime, but NOT the mtime.

diff hack.unix.c.old hack.unix.c
108c108
< 	if(buf.st_ctime < hbuf.st_ctime) {
---
> 	if(buf.st_mtime < hbuf.st_mtime) {