patch 8.1.0765: string format of a Blob can't be parsed back

Problem:    String format of a Blob can't be parsed back.
Solution:   Use 0z format.
diff --git a/src/eval.c b/src/eval.c
index af1021b..b31ed35 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -4258,6 +4258,8 @@
 			if (blob != NULL)
 			    ga_append(&blob->bv_ga,
 					 (hex2nr(*bp) << 4) + hex2nr(*(bp+1)));
+			if (bp[2] == '.' && vim_isxdigit(bp[3]))
+			    ++bp;
 		    }
 		    if (blob != NULL)
 			rettv_blob_set(rettv, blob);