patch 9.1.0979: VMS: type warning with $XDG_VIMRC_FILE

Problem:  VMS: type warning with $XDG_VIMRC_FILE
          (Zoltan Arpadffy)
Solution: add explicit (char_u *) type cast to mch_getenv() call

fixes: #16335

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index 00ba6f9..e63645d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    979,
+/**/
     978,
 /**/
     977,