irssi-0.8.18 breaks at least chat/irssi-icb and chat/irssi-xmpp.

According to the 0.8.18 changelog probably the following is needed:

 Modules will now require to define a
 ``void MODULENAME ## _abicheck(int *version)''
 method to ensure that they are compiled against the correct Irssi
 version.
