add command line option to suppress syslog messages when discards occur

	modified:   src/bruce/config.cc
	modified:   src/bruce/config.h
	modified:   src/bruce/input_dg/any_partition/any_partition_util.cc
	modified:   src/bruce/input_dg/any_partition/any_partition_util.h
	modified:   src/bruce/input_dg/any_partition/v0/v0_input_dg_reader.cc
	modified:   src/bruce/input_dg/any_partition/v0/v0_input_dg_reader.h
	modified:   src/bruce/input_dg/input_dg_common.cc
	modified:   src/bruce/input_dg/input_dg_common.h
	modified:   src/bruce/input_dg/input_dg_util.cc
	modified:   src/bruce/input_dg/old_v0_input_dg_reader.cc
	modified:   src/bruce/input_dg/old_v0_input_dg_reader.h
	modified:   src/bruce/input_dg/partition_key/partition_key_util.cc
	modified:   src/bruce/input_dg/partition_key/partition_key_util.h
	modified:   src/bruce/input_dg/partition_key/v0/v0_input_dg_reader.cc
	modified:   src/bruce/input_dg/partition_key/v0/v0_input_dg_reader.h
	modified:   src/bruce/msg_dispatch/receiver.cc
	modified:   src/bruce/router_thread.cc