Replace QMetaObject::invokeMethod with atomic operations

[hebasto]

No need to read/write a data member in one thread if it is atomic.

[promag]

An atomic bool would be enough?

Didn't want to mess with this in #120 because I think ballon filtering doesn't belong in transaction model. IMO the right place should be aware of what wallets are open.

[hebasto]

@promag

An atomic bool would be enough?

You're right. Reworked.

[promag]

This doesn't work: setProcessingQueuedTransactions needs to be enqueued and proceed in between transaction notifications.

[hebasto]

This doesn't work: setProcessingQueuedTransactions needs to be enqueued and proceed in between transaction notifications.

Why?

[promag]

Transaction notifications are enqueued in TransactionNotification::invoke and by the time they are processed setProcessingQueuedTransactions(false) was already called.

[hebasto]

You mean that setProcessingQueuedTransactions must be placed into the same event queue as updateTransaction, i.e., coordinated?

[promag]

@hebasto yes, processingQueuedTransactions() value is worthless.