patch 8.1.1905: cannot set all properties of the info popup

Problem:    Cannot set all properties of the info popup.
Solution:   Add popup_findinfo().  Rename popup_getpreview() to
            popup_findpreview().
diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index ee3291c..dceb1a7 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -5154,7 +5154,8 @@
 	else if (use_popup)
 	{
 	    wp = popup_find_info_window();
-	    // TODO: set position
+	    if (wp != NULL)
+		popup_show(wp);
 	}
 	else
 # endif