Renderer fixes and improvements.

src/pc.c

@@ -1132,6 +1132,13 @@ set_screen_size(int x, int y)
 }
 
 
+void
+reset_screen_size(void)
+{
+    set_screen_size(unscaled_size_x, efscrnsz_y);
+}
+
+
 void
 set_screen_size_natural(void)
 {