Re-add limit for fwait

Now restricted to adding/removing 900 seconds (15 minutes). There are no
valid reasons I can think of or that were given in -dev that would
require more time than this. 15 minutes is still likely too much and
from previous experience such long forced waits generally trigger a mass
exodus of players who would rather play a game than doing absolutely
nothing.

src/wolfgame.py

@@ -7405,6 +7405,7 @@ def fwait(cli, nick, chan, rest):
         extra = var.EXTRA_WAIT
 
     now = datetime.now()
+    extra = max(-900, min(900, extra))
 
     if now > var.CAN_START_TIME:
         var.CAN_START_TIME = now + timedelta(seconds=extra)