Begin locking down function types.

plugins/include/clientprefs.inc

@@ -182,7 +182,7 @@ functag public CookieMenuHandler(client, CookieMenuAction:action, any:info, Stri
  * @noreturn
  * @error				Invalid cookie handle.
  */
-native SetCookiePrefabMenu(Handle:cookie, CookieMenu:type, const String:display[], CookieMenuHandler:handler=CookieMenuHandler:-1, info=0);
+native SetCookiePrefabMenu(Handle:cookie, CookieMenu:type, const String:display[], CookieMenuHandler:handler=INVALID_FUNCTION, info=0);
 
 /**
  * Adds a new item to the client cookie settings menu.

plugins/include/dbi.inc

@@ -762,7 +762,7 @@ methodmap Transaction < Handle
 native SQL_ExecuteTransaction(
 		Handle:db,
 		Transaction:txn,
-		SQLTxnSuccess:onSuccess=SQLTxnSuccess:-1,
-		SQLTxnFailure:onError=SQLTxnFailure:-1,
+		SQLTxnSuccess:onSuccess = INVALID_FUNCTION,
+		SQLTxnFailure:onError = INVALID_FUNCTION,
 		any:data=0,
 		DBPriority:priority=DBPrio_Normal);

plugins/include/menus.inc

@@ -846,7 +846,7 @@ native RedrawMenuItem(const String:text[]);
  * @return				True on success, false on failure.
  * @error				Invalid client index, or radio menus not supported.
  */
-native bool:InternalShowMenu(client, const String:str[], time, keys=-1, MenuHandler:handler=MenuHandler:-1);
+native bool:InternalShowMenu(client, const String:str[], time, keys=-1, MenuHandler:handler=INVALID_FUNCTION);
 
 /**
  * Retrieves voting information from MenuAction_VoteEnd.

plugins/include/usermessages.inc

@@ -162,7 +162,7 @@ functag public MsgPostHook(UserMsg:msg_id, bool:sent);
  * @noreturn
  * @error				Invalid message index.
  */
-native HookUserMessage(UserMsg:msg_id, MsgHook:hook, bool:intercept=false, MsgPostHook:post=MsgPostHook:-1);
+native HookUserMessage(UserMsg:msg_id, MsgHook:hook, bool:intercept=false, MsgPostHook:post=INVALID_FUNCTION);
 
 /**
  * Removes one usermessage hook.