Update for untyped btcutil consts.

ok @davecgh
Don't return a double pointer.

This commit has no effect on the effective functionality since Go
automatically deferences pointers, but there is no reason to have a
double indirection when returning the reply for getmininginfo.
Correct QueueNotification comment.

This comment incorrectly said QueueMessage instead of QueueNotification.
Add new DNS seed for seeds.bitcoin.open-nodes.org.
Add full support for BIP0037 bloom filters.

This commit implements full support for filtering based on the filterload,
filteradd, filterclear, and merkleblock messages introduced by BIP0037.

This allows btcd to work seamlessly with SPV wallets such as BitcoinJ.

Original code by @dajohi.  Cleanup, bug fixes, and polish by @davecgh.
Switch btcctl to use btcutil.Amount.
Change AddAddressByIP to return an error.