mcc can now set memcached debug mode and has help

This patch let us set the debug mode on the memcached connection. Simply
pass --debug as an argument.  I have also added basic usage
documentation with --help, listing the interacting commands as well.

Example output:

$ php mcc.php --help
Usage:
	mcc.php [--debug]
	mcc.php --help

MemCached Command (mcc) is an interactive command tool that let you
interact
with the MediaWiki memcached cache.

Options:
	--debug Set debug mode on the memcached connection.
	--help  This help screen.

Interactive commands:
	get    : grabs something
	getsock: lists sockets
	set    : changes something
	delete : deletes something
	history: show command line history
	server : show current memcached server
	dumpmcc: shows the whole thing
	exit   : exit mcc
	quit   : exit mcc
	help   : help about a command

$

Change-Id: Ib4603eecbd6a8e6f3ba8bf3cf350c0e3df652d3b