popup: follow GDK_SCALE on HiDPI

The popup was 32-pixel rows whatever the display; next to 2x application
text it was small. Its metrics now scale with the daemon's GDK_SCALE,
the setting the applications use.

tests/popup_test.c

@@ -40,7 +40,7 @@ checkpadding(struct ct *t, u32int *img, Popup *p)
 void
 popup_layout(struct ct *t)
 {
-	static int tinyheight[] = {
+	int tinyheight[] = {
 		1, PopupPad, 2*PopupPad + Fontsz - 1,
 	};
 	static const struct {