patch 8.1.0601: a few compiler warnings

Problem:    A few compiler warnings.
Solution:   Add type casts. (Mike Williams)
diff --git a/src/version.c b/src/version.c
index a485b28..5db1001 100644
--- a/src/version.c
+++ b/src/version.c
@@ -800,6 +800,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    601,
+/**/
     600,
 /**/
     599,