Add helper function for disabled opcodes
Add helper function for disabled opcodes

Summary:
Add `IsOpcodeDisabled` helper function to see if an opcode
is supposed to be disabled or not

Test Plan: `make check`

Reviewers: deadalnix, jasonbcox, movrcx, matiu, #bitcoin_abc

Reviewed By: jasonbcox, #bitcoin_abc

Subscribers: teamcity

Differential Revision: https://reviews.bitcoinabc.org/D1209

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