patch 8.1.0802: negative index doesn't work for Blob

Problem:    Negative index doesn't work for Blob.
Solution:   Make it work, add a test. (closes #3856)
diff --git a/src/version.c b/src/version.c
index d662965..5b404ed 100644
--- a/src/version.c
+++ b/src/version.c
@@ -792,6 +792,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    802,
+/**/
     801,
 /**/
     800,