Re-added capability checking stuff. Boo. This needs refactored.

src/callbacks.py

@@ -1039,6 +1039,13 @@ class Commands(object):
 
     def _callCommand(self, command, irc, msg, *args, **kwargs):
         self.log.info('%s called by %q.', formatCommand(command), msg.prefix)
+        # XXX I'm being extra-special-careful here, but we need to refactor
+        #     this.
+        for name in command:
+            cap = checkCommandCapability(msg, self, name)
+            if cap:
+                irc.errorNoCapability(cap)
+                return
         try:
             try:
                 self.callingCommand = command