patch 7.4.1399
Problem:    The MS-DOS code does not build.
Solution:   Remove the old MS-DOS code.
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index 1321b7f..1f493ad 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -3758,7 +3758,7 @@
 
 	/* Check for environment variable */
 	if (*xp->xp_pattern == '$'
-#if defined(MSDOS) || defined(MSWIN)
+#if defined(MSWIN)
 		|| *xp->xp_pattern == '%'
 #endif
 		)