patch 8.2.0600: Vim9: cannot read or write w:, t: and b: variables

Problem:    Vim9: cannot read or write w:, t: and b: variables.
Solution:   Implement load and store for w:, t: and b: variables.
            (closes #5950)
diff --git a/src/version.c b/src/version.c
index ebe3b2c..d4a1f4f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    600,
+/**/
     599,
 /**/
     598,