singularization of irregularly pluralized monster types

Fix makesingular() to handle "vortices", "liches", and "fungi"
as suggested by <Someone> a while back; also "fungus".

doc/fixes34.1

@@ -111,6 +111,7 @@ usually stop mimicing if you polymorph while using #monster mimic capability
 under !GOLDOBJ, gold shouldn't disappear if you try to throw it at yourself
 under !GOLDOBJ, remove temp gold from inventory during restore
 Staff of Aesculapius did not always cure sliming
+correct singularization of fungi, liches, vortices
 
 
 Platform- and/or Interface-Specific Fixes