Added CallVoteFailed UserMessage for L4D and L4D2
nativevotes.inc now has a new NativeVotesCallFailType: NativeVotesCallFail_Generic. Necessary for L4D/L4D2 support.
DisplayVoteFail should now work on L4D.
L4D: Casting a vote now sends the VoteRegistered usermessage instead of the vote_cast_yes or vote_cast_no events.
L4D/L4D2: NativeVotes_DisplayCallVoteFail should now work on these, but probably only for NativeVotesCallFail_Generic and NativeVotesCallFail_Loading.