This commit has several important work and now most of the binary works
without slaves.

Gtm_util and pgxc_monitor is now imported to pgxc_ctl so that it can run
without any contrib binaries.

	modified:   coord_cmd.c
	modified:   datanode_cmd.c
	modified:   do_command.c
	new file:   gtm_util.c
	new file:   gtm_util.h
	new file:   mcxt.c
	new file:   monitor.c
	new file:   monitor.h
	modified:   pgxc_ctl.c