Acceptance as an IPC call

[jjcnn]

The blockchain handles transition execution as a black box, so when a contract performs an accept statement the blockchain doesn't immediately transfer the funds from _sender to _this_address. Rather, the funds are not transferred until the transition completes successfully.

This means that Scilla needs to "mask" the remote read of _sender._balance, because the underlying IPC fetch gives us the balance without the deduction of the accepted funds.

It would be much easier if we could invoke the transfer when Scilla executed an accept statement, so that we could simply read the balance directly without having to jump through any hoops.

[jjcnn]

Made obsolete by #1032