patch 8.1.0422: cannot create map file with MinGW

Problem:    Cannot create map file with MinGW.
Solution:   Add support for $MAP. (Ken Takata, closes #3460)
diff --git a/src/version.c b/src/version.c
index c541dc9..372fe87 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    422,
+/**/
     421,
 /**/
     420,