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>

src/os_unix.h

@@ -250,7 +250,7 @@ typedef struct dsc$descriptor   DESC;
 #endif
 
 #ifndef XDG_VIMRC_FILE
-# define XDG_VIMRC_FILE (mch_getenv("XDG_CONFIG_HOME") \
+# define XDG_VIMRC_FILE (mch_getenv((char_u *)"XDG_CONFIG_HOME") \
 	? "$XDG_CONFIG_HOME/vim/vimrc" \
 	: "~/.config/vim/vimrc")
 #endif

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    979,
 /**/
     978,
 /**/