This patch handles version collisions of binary archives. If a binary
archive for an (automatically) updated src-archive version already
exists in the depot, the extract tool removes the binary archive because
its existing content may stem from another src content (a version from a
different topic branch). This ensures that the new version is always
built, not skipped, when 'UPDATE_VERSIONS=1 REBUILD=' is specified.
Fixes#3267
This patch changes the depot layout such that each archive is
represented as a directory that contains the versions of the archive as
subdirectories.
Issue #2610
