patch 8.1.0228: dropping files is ignored while Vim is busy

Problem:    Dropping files is ignored while Vim is busy.
Solution:   Postpone the effect of dropping files until it's safe.
diff --git a/src/version.c b/src/version.c
index 6528355..8b31adb 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    228,
+/**/
     227,
 /**/
     226,