Set mobile registered event when odd egg has been received.

We will use this event in place of PokeCom Center activation checks that have been removed.
Replace all "special $00a0" checks with event checks.

This routine checked if the mobile was registered in the Japanese ROM, however it always returns false in the English one.
Battle tower reference in EcruteakPokeCenter1F makes more sense after beating the Kimono Girls
Battle tower references make more sense when the player has actually battled there.
Restore PokeCom center reference in Celadon city