Add HookPluginUnload() and UnhookPluginUnload() functions

plugins/include/sourcemod.inc

@@ -84,6 +84,13 @@ enum APLRes
 	APLRes_SilentFailure    /**< Plugin shouldn't load but do so silently */
 };
 
+/**
+ * Called when a plugin unloaded.
+ * 
+ * @param plugin        Plugin Handle who unloaded.
+ */
+typedef PluginUnloaded = function void (Handle plugin);
+
 methodmap GameData < Handle
 {
 	// Loads a game config file.
@@ -319,6 +326,26 @@ native bool GetPluginInfo(Handle plugin, PluginInfo info, char[] buffer, int max
  */
 native Handle FindPluginByNumber(int order_num);
 
+/**
+ * Creates a hook for when a plugin unloaded.
+ * 
+ * @param plugin        Plugin Handle to hook.
+ * @param callback      An PluginUnloaded function pointer.
+ * 
+ * @return              True on success, false otherwise.
+ */
+native bool HookPluginUnload(Handle plugin, PluginUnloaded callback);
+
+/**
+ * Removes a hook for when a plugin unloaded.
+ * 
+ * @param plugin        Plugin Handle to hook.
+ * @param callback      An PluginUnloaded function pointer.
+ * 
+ * @return              True on success, false otherwise.
+ */
+native bool UnhookPluginUnload(Handle plugin, PluginUnloaded callback);
+
 /**
  * Causes the plugin to enter a failed state.  An error will be thrown and
  * the plugin will be paused until it is unloaded or reloaded.