lua.wire.fifo.pull
memo = fifo:pull()
memo = thread:pull()
Pull memo out of this fifo.
If this is a memo for us to deal with memo.state will be set to "got"
If this is a result we will return the sent memo with memo.result set to the reply data and the memo state will be changed to "result".
memo may be ignored for now and dealt with later by finding it in wire.memos.
This is useful if you are waiting for a specific reply and want to keep pulling until you find it.
Returns nil if there is no memo available.
May raise an error if we get a reply with an id that we do not recognize.