NSSC Solana updates

[smoelius]

Several language fixes, as well as bug fixes to the owner and signer check examples.

[nop4e71]

I think we need to restructure the missing ownership.
Perhaps something like:

Pseudo code
instruction pay_escrow(accounts)
  if accounts.state.escrow_state == complete {
    tokens.transfer(escrow_vault, accounts.state.escrow_receiver, accounts.state.escrow_amount); 
  }

The working principle is some sort of escrow contract with a state and vault account.
Because of the missing ownership check on the passed state account, it is possible to make the contract believe the escrow is complete and transfer funds to the receiver.

[CLAassistant]

All committers have signed the CLA.

[smoelius]

From our perspective, this is ready for review, @montyly.