patch 8.0.1717: C89 check causes too much trouble

Problem:    C89 check causes too much trouble.
Solution:   Remove enforcing C89 for now.
diff --git a/src/version.c b/src/version.c
index 1c6c15d..207048f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -763,6 +763,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1717,
+/**/
     1716,
 /**/
     1715,