GLK: FROTZ: Fix drawing graphics in Zork Zero vs Arthur

In Zork Zero, grahpics drawn to window 0 (the text buffer)
are always treated as being interleaved with the text.
Whereas in Arthur, the title screens are drawn to window 0,
so have to be drawn to the background

engines/glk/frotz/processor_windows.cpp

@@ -49,8 +49,9 @@ void Processor::z_draw_picture() {
 	flush_buffer();
 
 	Window &win = _wp[_wp._cwin];
-	if (_wp._cwin == 0) {
-		// Embedded picture within the text area
+	if (_storyId == ZORK_ZERO && _wp._cwin == 0) {
+		// WORKAROUND: Zork Zero has pictures for graphics embedded in the text with specific
+		// co-prdinates. We need to reset it to 0,0 to flag it should be drawn at the cursor
 		x = y = 0;
 	} else {
 		assert(x && y);