When replacing a report with a smaller one, the corresponding ROM
dataspace should not contain any traces of the old report. Otherwise,
the consumer of the ROM dataspace may mistake the stale content as
meaningful information. This is particularly annoying when manually
inspecting reports. This patch overwrites the stale content with zeros.
The new Rom_session::update function can be used to request the update of
an existing ROM dataspace. If the new data fits into the existing
dataspace, a subsequent call of 'dataspace' can be omitted. This way,
ROM dataspace updates don't suffer from page-fault-handling costs that
would occur when replacing the dataspace with each update.
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082
