Input-triggered transaction expiry

[instagibbs]

@ademan

@josh

CLTV enforces a minimum nLockTime, so I don’t believe this works. We need to enforce a maximum nLockTime. This is probably best accomplished with nLockTime introspection (ex: OP_LOCKTIME) and OP_LESSTHAN.

I believe he meant in conjunction with OP_TX and math on the stack