[ADD/WIP] Congestion, basic ad-hoc commands

Woah, took me a while, eh? Next up, getting forms!

src/include/Parsee.h

@@ -123,6 +123,14 @@ extern void * ParseeXMPPThread(void *data);
  * Modifies: NONE */
 extern XMLElement * ParseeAwaitStanza(char *identifier, int64_t ts);
 
+/** Returns the amount of unprocessed stanzas in the XMPP thread, which 
+ * can be used by admins to guess load.
+ * --------
+ * UB-If: called in the XMPP dispatcher thread itself
+ * Returns: amount of stanzas in the FIFO
+ * Modifies: NONE */
+extern size_t ParseeCongestion(void);
+
 /* Finds the room a DM is associated to, from a Matrix user and a Jabber 
  * ID. */
 extern char * ParseeFindDMRoom(ParseeData *data, char *mxid, char *jid);