New module hooks (#69)

New module hooks (#69)

* Add SPAMWARN module hook

CHOOK_SPAMWARN is called from s_user.c and channel.c during spam warnings to opers

Params: 4: (aClient *source, int type, int max_targets, char *target_name)

Returns: int (FLUSH_BUFFER would prevent the normal message from being sent)

* Add ONACCESS module hook

CHOOK_ONACCESS is called from s_user.c during m_user (in general, it is called before CHOOK_POSTACCESS and after CHOOK_PREACCESS)

Params: 5: (aClient *, char *username, char *host, char *server, char *realname)
Returns: int (FLUSH_BUFFER can block the m_user call)