Merge from vendor branch BIND:
Add BIND 9.2.4rc7.
Notable changes:
1643. [bug] dns_db_closeversion() could leak memory / node
references. [RT #11163]
1650. [bug] dig, nslookup: flush standard out after each command.
1654. [bug] isc_result_totext() contained array bounds read
error.
1681. [bug] Only set SO_REUSEADDR when a port is specified in
isc_socket_bind(). [RT #11742]
1686. [bug] Named sent a extraneous NOTIFY when it received a
redundant UPDATE request. [RT #11943]
1687. [bug] Race condition in dispatch. [RT #10272]
1690. [bug] Delay detaching view from the client until UPDATE
processing completes when shutting down. [RT #11714]