Register callvote command as an alias for vote

[execut4ble]

Adrenaline Gamer has the callvote command as an alternative to vote, I know for a fact that this alias is sometimes used by some other AMXX plugins to issue player votes, would be nice to support it.

[rtxa]

Thanks! A little bit offtopic but I really wish we only have vote as the main vote command. Having the syntax <vote> <value> is ambiguous because it can clash with other commands or game modes but I understand that people rely on this behaviour.