- [script/standard.o] IsStandard
- [main.o] IsStandardTx
- [main.o] AreInputsStandard

coming from btc@9238ecb41752e097443d0bc117df35ebd4ac932e

Previously unlike other transaction types the TX_SCRIPTHASH would not
clear vSolutionsRet, which means that unlike other transaction types if
it was called twice in a row you would get the result of the previous
invocation as well.

Previously this was an inline test where the specificity was probably judged
overly specific. As a class method it makes sense to maintain consistency.

And replace some magic values with their constant equivalents.

Excludes changes to the following functions we don't have:

- ExtractPubKey (bitcoin#6415)
- IsCompressedPubKey (bitcoin#8499)

The current code contains a rather complex script template matching engine,
which is only used for 3 particular script types (P2PK, P2PKH, multisig).
The first two of these are trivial to match for otherwise, and a specialized
matcher for multisig is both more compact and more efficient than a generic
one.

The goal is being more flexible, so that for example larger standard multisigs
inside SegWit outputs are more easy to implement.

As a side-effect, it also gets rid of the pseudo opcodes hack.

coming from btc@c814e2e7e81fd01fcb07f4a28435741bdc463801