Fix pg_dump to do the right thing when escaping the contents of large objects.

The previous implementation got it right in most cases but failed in one:
if you pg_dump into an archive with standard_conforming_strings enabled, then
pg_restore to a script file (not directly to a database), the script will set
standard_conforming_strings = on but then emit large object data as
nonstandardly-escaped strings.

At the moment the code is made to emit hex-format bytea strings when dumping
to a script file.  We might want to change to old-style escaping for backwards
compatibility, but that would be slower and bulkier.  If we do, it's just a
matter of reimplementing appendByteaLiteral().

This has been broken for a long time, but given the lack of field complaints
I'm not going to worry about back-patching.

src/bin/pg_dump/dumputils.c

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/bin/pg_dump/dumputils.c,v 1.47 2009/07/14 20:24:10 tgl Exp $
+ * $PostgreSQL: pgsql/src/bin/pg_dump/dumputils.c,v 1.48 2009/08/04 21:56:08 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -325,6 +325,55 @@ appendStringLiteralDQ(PQExpBuffer buf, const char *str, const char *dqprefix)
 }
 
 
+/*
+ * Convert a bytea value (presented as raw bytes) to an SQL string literal
+ * and append it to the given buffer.  We assume the specified
+ * standard_conforming_strings setting.
+ *
+ * This is needed in situations where we do not have a PGconn available.
+ * Where we do, PQescapeByteaConn is a better choice.
+ */
+void
+appendByteaLiteral(PQExpBuffer buf, const unsigned char *str, size_t length,
+				   bool std_strings)
+{
+	const unsigned char *source = str;
+	char	   *target;
+
+	static const char hextbl[] = "0123456789abcdef";
+
+	/*
+	 * This implementation is hard-wired to produce hex-format output.
+	 * We do not know the server version the output will be loaded into,
+	 * so making an intelligent format choice is impossible.  It might be
+	 * better to always use the old escaped format.
+	 */
+	if (!enlargePQExpBuffer(buf, 2 * length + 5))
+		return;
+
+	target = buf->data + buf->len;
+	*target++ = '\'';
+	if (!std_strings)
+		*target++ = '\\';
+	*target++ = '\\';
+	*target++ = 'x';
+
+	while (length-- > 0)
+	{
+		unsigned char c = *source++;
+
+		*target++ = hextbl[(c >> 4) & 0xF];
+		*target++ = hextbl[c & 0xF];
+	}
+
+	/* Write the terminating quote and NUL character. */
+	*target++ = '\'';
+	*target = '\0';
+
+	buf->len = target - buf->data;
+}
+
+
 /*
  * Convert backend's version string into a number.
  */