old system (for example, the meaning of 'a') has yet to be restored. In the
new scheme, this will be done by definition a function outside of the value
expression logic, rather than the tight coupling between journal innards and
value expressions that occurred in 2.x.
Complete changed the way format strings are handled. They are now
compiled first, which is far more efficient than what was being done
before.
Also, there is now a global ledger::commodity_t::commodities map,
which saves me from having to pass the current journal around to a
zillion different functions, for the sole purpose of making sure that
all commodity symbols that are parsed refer to the same commodity
object.
