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.

win.c

@@ -206,7 +206,11 @@ wininit(void)
 	xcb_randr_query_version_cookie_t rc;
 	xcb_randr_query_version_reply_t *rr;
 	const xcb_query_extension_reply_t *rext;
+	char *scale;
 
+	scale = getenv("GDK_SCALE");
+	if(scale != nil && atoi(scale) > 1)
+		popupscale = min(atoi(scale), 4);
 	conn = xcb_connect(nil, &n);
 	if(xcb_connection_has_error(conn)){
 		fprint(2, "strans: popup disabled: cannot connect to X display\n");