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
Doing a -reindex on a datadir of a different client gives us thousands
of small blk files, which may result in us hitting the max simultaneous
open files limit.
This change forces us to flush the list a bit more aggressively and
close open files.
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