patch 8.0.1608: Win32: directx not enabled by default

Problem:    Win32: directx not enabled by default.
Solution:   Change Makefile to enable directx by default. (Ken Takata)
diff --git a/src/version.c b/src/version.c
index e7e3f49..7e12ce7 100644
--- a/src/version.c
+++ b/src/version.c
@@ -767,6 +767,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1608,
+/**/
     1607,
 /**/
     1606,