Add .prism as model file extension to GUI.

git-svn-id: https://www.prismmodelchecker.org/svn/prism/prism/trunk@4619 bbc10eb1-c90d-0410-af57-cb519fbb1720

prism/src/userinterface/model/GUIMultiModel.java

@@ -1054,7 +1054,8 @@ public class GUIMultiModel extends GUIPlugin implements PrismSettingsListener
 		}
 
 		modelFilters = new GUIPrismFileFilter[GM_ENABLED ? 3 : 2];
-		modelFilters[FILTER_PRISM_MODEL] = new GUIPrismFileFilter("PRISM models (*.pm, *.nm, *.sm)");
+		modelFilters[FILTER_PRISM_MODEL] = new GUIPrismFileFilter("PRISM models (*.prism, *.pm, *.nm, *.sm)");
+		modelFilters[FILTER_PRISM_MODEL].addExtension("prism");
 		modelFilters[FILTER_PRISM_MODEL].addExtension("pm");
 		modelFilters[FILTER_PRISM_MODEL].addExtension("nm");
 		modelFilters[FILTER_PRISM_MODEL].addExtension("sm");