If you really must have a useless $wgUseRCPatrol option, might as well use it

If you really must have a useless $wgUseRCPatrol option, might as well use it
consistently everywhere to ensure that setting it to 0 actually does disable the
feature.  Also, tell the user that it is disabled if they happen to follow a link
with &action=markpatrolled in it.  Additionally, make &action=markpatrolled say
"log in required" if the user is not logged in.