gui/osd_helpers.cpp/h: add signal OnAfterChangeResolution

Adds possibility to use any methods after changed resolution without
any changes on COsdHelpers class.
Implementation is possible directly from other objects that need this.

src/gui/osd_helpers.cpp

@@ -123,6 +123,7 @@ void COsdHelpers::changeOsdResolution(uint32_t mode, bool automode/*=false*/, bo
 			CNeutrinoApp::getInstance()->StartSubtitles();
 		}
 	}
+	OnAfterChangeResolution();
 }
 #else
 void COsdHelpers::changeOsdResolution(uint32_t, bool, bool)