gas spores attempting to attack

From a bug report, but pulls back" while successfully
praying.  Gas spores' only "attack" is to explode when dying, so the code
that checks whether the monster has any attack needs to handle AT_BOOM as
a special case.  Unfortunately this change means that you won't interrupt
an occupation when a gas spore approaches, and a subsequent kill by your
pet might end up causing you harm while still occupied.  The callers of
`noattacks()' are messy enough that I didn't want to try to address that.

     This also moves noattacks() from mhitm.c to somewhere more sensible.

doc/fixes34.4

@@ -56,6 +56,7 @@ destroying a worn item via dipping in burning oil would not unwear/unwield
 	the item properly, possibly leading to various strange behaviors
 avoid a panic splitbill when shopkeeper is trapped by the door
 grammar tidbit for message given when eating tainted meat is also cannibalism
+gas spores shouldn't be described as "unable to attack" while hero is praying
 
 
 Platform- and/or Interface-Specific Fixes