vesper_cmcp: Added basic implementation of heartbeat to server.
vesper_cmcp: Added vsp_cmcp_common to send messages to sockets.
vesper_util: Removed vsp_time functions from API as they are private.
vesper_cmcp: Fixed wrong return values in case of failure.
vesper_util: Added vsp_random to produce pseudo-random numbers.
vesper_cmcp: Removed underscore prefix for private function in server.