Instead of building a full copy of a CTransaction being signed, and
then modifying bits and pieces until its fits the form necessary
for computing the signature hash, use a wrapper serializer that
only serializes the necessary bits on-the-fly.
This makes it easier to see which data is actually being hash,
reduces load on the heap, and also marginally improves performances
(around 3-4us/sigcheck here). The performance improvements are much
larger for large transactions, though.
The old implementation of SignatureHash is moved to a unit tests,
to test whether the old and new algorithm result in the same value
for randomly-constructed transactions.
This change moves test data into the binaries rather than reading them from
the disk at runtime.
Advantages:
- Tests become distributable
- Cross-compile friendly. Build on one machine and execute in an arbitrary
location on another.
- Easier testing for backports. Users can verify that tests pass without having
to track down corresponding test data.
- More trustworthy test results and easier quality assurance as tests make
fewer assumptions about their environment.
- Tests could theoretically run at client/daemon startup and exit on failure.
Disadvantages:
- Required 'hexdump' build-dependency. This is a standard bsd tool that should
be usable everywhere. It is likely already installed on all build-machines.
- Tests can no longer be fudged after build by altering test-data.
