Make groups be 64-bits (bug #3351, with mods)

channel.c

channels/chan_agent.c

channels/chan_mgcp.c

channels/chan_modem.c

channels/chan_sip.c

channels/chan_skinny.c

channels/chan_zap.c

include/asterisk/channel.h

include/asterisk/utils.h

include/asterisk/vmodem.h

utils.c