Rerip X/Y Pokémon icons.

All eighteen of these Arceus icons are identical, but the game does
actually point at that icon eighteen times, and it was the only
Pokémon left for which we didn't have separate icons for separate
forms.  It'll be nice not having to special-case it.

The sprites in right/ are actually not mirrored in the games' guts, but
they're only ever displayed mirrored — that's the whole point, even — so
I flipped them.  (I built the flipping right into the ripper, so they
still have immaculate palettes, sBIT chunks, etc.)