fix #H4272 - "you turn into a Elvenking"

fix #H4272 - "you turn into a Elvenking"

Polyself with gender change into a creature with fixed gender
would deliver a message containing "a <creature>" regardless of
whether "an" was warranted.

(Into any creature which supports both genders it yielded
"a male <creature>" or "a female <creature>" so "an" was never
needed.  And when no gender change was involved, it used an()
so got "a <creature>" or "an <creature>" as applicable.)