patch 7.4.1399
Problem: The MS-DOS code does not build.
Solution: Remove the old MS-DOS code.
diff --git a/src/macros.h b/src/macros.h
index 012def6..ffc29f0 100644
--- a/src/macros.h
+++ b/src/macros.h
@@ -226,7 +226,7 @@
#if defined(UNIX) || defined(VMS) /* open in rw------- mode */
# define mch_open_rw(n, f) mch_open((n), (f), (mode_t)0600)
#else
-# if defined(MSDOS) || defined(MSWIN) /* open read/write */
+# if defined(MSWIN) /* open read/write */
# define mch_open_rw(n, f) mch_open((n), (f), S_IREAD | S_IWRITE)
# else
# define mch_open_rw(n, f) mch_open((n), (f), 0)