Revert "COMMON: Change way the Singleton instances are instantiated"

This reverts commit eefa72afa1.

With this patch ConfigManager is broken.

backends/plugins/elf/shorts-segment-manager.cpp

@@ -33,6 +33,10 @@ extern char __plugin_hole_start;	// Indicates start of hole in program file for
 extern char __plugin_hole_end;		// Indicates end of hole in program file
 extern char _gp[];					// Value of gp register
 
+namespace Common {
+DECLARE_SINGLETON(ShortSegmentManager);	// For singleton
+}
+
 ShortSegmentManager::ShortSegmentManager() {
 	_shortsStart = &__plugin_hole_start ;	//shorts segment begins at the plugin hole we made when linking
 	_shortsEnd = &__plugin_hole_end;		//and ends at the end of that hole.