symbolic-ref, update-ref: do not refuse reflog message with LF

Earlier these tools refused to create a reflog entry when the
message given by the calling Porcelain had a LF in it, partially
to keep the file format integrity of reflog file, which is
one-entry-per-line.  These tools should not be dictating such a
policy.

Instead, let the codepath to write out the reflog entry worry
about the format integrity and allow messages with LF in them.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-symbolic-ref.c

@@ -43,8 +43,6 @@ int cmd_symbolic_ref(int argc, const char **argv, const char *prefix)
 			msg = argv[1];
 			if (!*msg)
 				die("Refusing to perform update with empty message");
-			if (strchr(msg, '\n'))
-				die("Refusing to perform update with \\n in message");
 		}
 		else if (!strcmp("--", arg)) {
 			argc--;

builtin-update-ref.c

@@ -23,8 +23,6 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 			msg = argv[++i];
 			if (!*msg)
 				die("Refusing to perform update with empty message.");
-			if (strchr(msg, '\n'))
-				die("Refusing to perform update with \\n in message.");
 			continue;
 		}
 		if (!strcmp("-d", argv[i])) {