Pull request for "getmemorypool" RPC call

(Moving here because forum thread at https://bitcointalk.org/index.php?topic=39088 didn't yield much discussion)

Pull request: https://github.com/bitcoin/bitcoin/pull/476 Diff: https://github.com/bitcoin/bitcoin/pull/476/files

This was originally a patch that returned bitcoin's memory pool as list of transaction hashes and the amount of total fees, but evolved into a full alternative to the "getwork" RPC call for clients that create their own generation transactions.

Like getwork, this call calls CreateBlock and returns parts of it for mining, but instead of generating its own merkle tree, it returns all the information needed to create a generation transaction in addition to the full contents of other transactions that should be included. It, as is, has had some testing done with p2pool - it resulted the first p2pool generated block with transactions: http://blockexplorer.com/block/00000000000002436bd2ae60d67d6fc0dce44deba2ad739619a3d364f6283e64

Help text:

getmemorypool [data]
If [data] is not specified, returns data needed to construct a block to work on:
  "version" : block version
  "previousblockhash" : hash of current highest block
  "transactions" : contents of non-coinbase transactions that should
be included in the next block
  "coinbasevalue" : maximum allowable input to coinbase transaction,
including the generation award and transaction fees
  "time" : timestamp appropriate for next block
  "bits" : compressed target of next block
If [data] is specified, tries to solve the block and returns true if
it was successful.

Thank you, Forrest Voight