patch 8.1.1645: cannot use a popup window for a balloon

Problem:    Cannot use a popup window for a balloon.
Solution:   Add popup_beval().  Add the "mousemoved" property.  Add the
            screenpos() function.

src/normal.c

@@ -2328,6 +2328,9 @@ do_mouse(
 	    profile_setlimit(p_bdlay, &bevalexpr_due);
 	    bevalexpr_due_set = TRUE;
 	}
+#endif
+#ifdef FEAT_TEXT_PROP
+	popup_handle_mouse_moved();
 #endif
 	return FALSE;
     }