patch 8.0.1663: cannot build without multi-byte feature

Problem:    Cannot build without multi-byte feature.
Solution:   Add #ifdef.
diff --git a/src/version.c b/src/version.c
index 4b9761f..4d19b47 100644
--- a/src/version.c
+++ b/src/version.c
@@ -763,6 +763,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1663,
+/**/
     1662,
 /**/
     1661,