This introduces a new BlockHeader helper class which Block and
MutableBlock can both produce, which helps a lot of methods to
be ported to no longer be dependent on us using a MutableBlock
object, which is too costly to use when we have no intention
to alter the block.
For transaction::checkTransaction():
this in practice avoids lots of mallocs and overhead while doing
transaction checks.
For merkleroot, the same benefits. Avoiding copying and mallocs.
This moves the class CBlockFileInfo from main.h to the BlocksDB_p.h
file as that is the class where it is mostly used.
There is a global variable in main.{h|cpp} left but since that is
strictly limited to main.cpp it made no sense to details slip out
via the massively overused main.h
These are technically static libs, but not in any way shared libs.
They are used solely only by this repo and really only by the hub.
Most important, no header files are installed and basically none of
the normal rules for reusable libraries are applied to these files.
tomFlowee