patch 9.0.0430: cannot use repeat() with a blob

Problem:    Cannot use repeat() with a blob.
Solution:   Implement blob repeat. (closes #11090)
diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index 12d62a6..0126340 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -471,7 +471,8 @@
 					remove bytes {idx}-{end} from {blob}
 remove({dict}, {key})		any	remove entry {key} from {dict}
 rename({from}, {to})		Number	rename (move) file from {from} to {to}
-repeat({expr}, {count})		String	repeat {expr} {count} times
+repeat({expr}, {count})		List/Blob/String
+					repeat {expr} {count} times
 resolve({filename})		String	get filename a shortcut points to
 reverse({list})			List	reverse {list} in-place
 round({expr})			Float	round off {expr}
@@ -7294,8 +7295,8 @@
 		result.  Example: >
 			:let separator = repeat('-', 80)
 <		When {count} is zero or negative the result is empty.
-		When {expr} is a |List| the result is {expr} concatenated
-		{count} times.  Example: >
+		When {expr} is a |List| or a |Blob| the result is {expr}
+		concatenated {count} times.  Example: >
 			:let longlist = repeat(['a', 'b'], 3)
 <		Results in ['a', 'b', 'a', 'b', 'a', 'b'].