patch 9.0.1420: build failure because SIZE_MAX is not defined

Problem:    Build failure because SIZE_MAX is not defined.
Solution:   Define SIZE_MAX when missing. (John Marriott)
diff --git a/src/version.c b/src/version.c
index 379980a..32c39be 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1420,
+/**/
     1419,
 /**/
     1418,