msummon,nasty result counts (trunk only)

Reported in Dec'04 by <email deleted>, the
monster spell "summon nasties" could mistakenly give a message of "a
monster appears" instead of "monsters appear" when more that one monster
gets summoned.  Some of the candidate monsters for nasty() can produce a
group from makemon(), as can ones for msummon() which nasty() sometimes
calls in Gehennom.  Compare the number of monsters before and after the
creation attempt(s) instead of assuming makemon() creates one at a time.

     I don't know whether other routines face the same mis-count issue,
but I suspect there may be several.

doc/fixes35.0

@@ -218,6 +218,7 @@ hero undergoing semi-controlled polymorph won't also undergo sex change
 when doppelgangers taking on new shape don't specifically pick nasty monster
 	or role monster, bias the random form towards humanoid
 salamanders can use green slime corpses to cure themselves of petrification
+feedback about summoned monsters may use singular when it should use plural
 
 
 Platform- and/or Interface-Specific Fixes