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.
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.
To get the advantages of faster GetSerializeSize() implementations
back that were removed in "Make GetSerializeSize a wrapper on top of
CSizeComputer", reintroduce them in the few places in the form of a
specialized Serialize() implementation. This actually gets us in a
better state than before, as these even get used when they're invoked
indirectly in the serialization of another object.
Remove the nType and nVersion as parameters to all serialization methods
and functions. There is only one place where it's read and has an impact
(in CAddress), and even there it does not impact any of the recursively
invoked serializers.
Instead, the few places that need nType or nVersion are changed to read
it directly from the stream object, through GetType() and GetVersion()
methods which are added to all stream classes.
Given that in default GetSerializeSize implementations created by
ADD_SERIALIZE_METHODS we're already using CSizeComputer(), get rid
of the specialized GetSerializeSize methods everywhere, and just use
CSizeComputer. This removes a lot of code which isn't actually used
anywhere.
For CCompactSize and CVarInt this actually removes a more efficient
size computing algorithm, which is brought back in a later commit.
