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)

src/gui/osd_helpers.h

@@ -2,12 +2,14 @@
 #ifndef __osd_helpers__
 #define __osd_helpers__
 
+#include <sigc++/signal.h>
+
 enum {
 	OSDMODE_720  = 0,
 	OSDMODE_1080 = 1
 };
 
-class COsdHelpers
+class COsdHelpers : public sigc::trackable
 {
 	private:
 
@@ -23,6 +25,7 @@ class COsdHelpers
 		int  getVideoSystem();
 		uint32_t getOsdResolution();
 		int setVideoSystem(int newSystem, bool remember = true);
+		sigc::signal<void> OnAfterChangeResolution;
 };