viewing geno'd monsters at "genocide what?" prompt

At either of the genocide prompts,
|What type of monster do you want to genocide?
or
|What class of monsters do you want to genocide?
answering "?<return>" will show the list of monster types that have
already been genocided, then re-prompt.

doc/fixes3-7-0.txt

@@ -2234,6 +2234,9 @@ new status highlight rule type for hitpoints:  "criticalhp" rule overrides
 	hit point rules if current HP is so low that prayer will consider it
 	to be major problem; applies to hitpointbar as well as HP status
 high skill level in martial arts or bare-handed combat sometimes hits twice
+answering '?<return>' at the "genocide what?" prompt (for either monster class
+	or single species) runs the #genocided command to show what types of
+	monsters have already been genocided and then re-prompts
 
 
 Platform- and/or Interface-Specific New Features