Fix removal of DCC_PROC-type plugin addins

The declaration of dcc_dllcommands in modules.c was wrong - add it to dcc.h so it's checked against the definition in dcc.c
and include it from there.

The DCC_dllcommands structure isn't structured like a "List2" so remove_module() doesn't work - use remove_from_list_ext().

include/dcc.h

@@ -8,6 +8,10 @@
 #ifndef __dcc_h_
 #define __dcc_h_
 
+#include "struct.h"
+
+extern DCC_dllcommands *dcc_dllcommands;
+
 	/* 
 	 * these are all used in the bot_link layer. the dcc_printf is used in
 	 * a few other places as well. ie dcc.c