Script: add OP_VERIF, OP_VERNOTIF to disabled ops

not explicitly tested together with the other disabled opcodes in bitcoind for
some reason
Script: pull checkEmptyIfStack into evalAll
Script: altStack is not shared between executions
Script: handle OP_VER correctly, add checkPushOps

checkPushOps currently disabled, the conditions under which it is executed are a
a little tricky