OP_CHECKMULTISIGVERIFY

Apparently this has been missing all the time, was just triggered by testnet tx
b5cd9e999fb51e29ab741b1e1732f1d4d038bc493ffbced85a252533a2c2ab0c

Seems easy enough to implement, but the script execution still fails, because the OP_CHECKMULTISIG leaves the stack as [2, 1].