re-implement faction:add_message for Lua.

only ancient xmas scripts were using it, but it's a useful function to have.

src/bind_faction.c

@@ -22,6 +22,7 @@ without prior permission by the authors of Eressea.
 #include <kernel/unit.h>
 #include <kernel/item.h>
 #include <kernel/faction.h>
+#include <kernel/messages.h>
 #include <kernel/plane.h>
 #include <kernel/race.h>
 #include <kernel/region.h>
@@ -211,6 +212,15 @@ static int tolua_faction_renumber(lua_State * L)
   return 0;
 }
 
+static int tolua_faction_addnotice(lua_State * L)
+{
+    faction *self = (faction *)tolua_tousertype(L, 1, 0);
+    const char *str = tolua_tostring(L, 2, 0);
+
+    addmessage(NULL, self, str, MSG_MESSAGE, ML_IMPORTANT);
+    return 0;
+}
+
 static int tolua_faction_get_objects(lua_State * L)
 {
   faction *self = (faction *) tolua_tousertype(L, 1, 0);
@@ -563,8 +573,9 @@ void tolua_faction_open(lua_State * L)
         .property("x", &faction_getorigin_x, &faction_setorigin_x)
         .property("y", &faction_getorigin_y, &faction_setorigin_y)
 
-        .def("add_notice", &faction_addnotice)
 #endif
+      tolua_function(L, TOLUA_CAST "add_notice", &tolua_faction_addnotice);
+
       tolua_variable(L, TOLUA_CAST "objects", tolua_faction_get_objects,
         NULL);
     }