IsPegout should enforce that all opcodes are ≤ OP_PUSHDATA4

[apoelstra]

to match rust-elements. Related to #596

[roconnor-blockstream]

At this point it is probably sensible to change data.size() == 0 to opcode > OP_PUSHDATA4 at

elements/src/script/script.cpp

Line 222 in f084479

if (!GetOp(pc, opcode, data) || data.size() == 0 ) {

and allow empty pegout_scriptPubKeys in the definition of a pegout.

This will involve reverting the change in rust-elements to reallow empty pegout_scriptPubKeys to keep everyone in sync.

[stevenroose]

Closed as per #610