packagefs: Remove PackageDataV1 from PackageData.

Now that we never access V1 packages in here, we don't need this.
This saves *24* bytes off the size of the class, which is
extremely significant as not only every PackageFile instance
has an instance of this class, but every PackageNode does too;
so the savings from this change is probably in the MB.

packagefs: PackageData: Fix copy and paste error

hpkg format: compress the whole heap

Instead of handling compression for individual file/attribute data we
do now compress the whole heap where they are stored. This
significantly improves compression ratios. We still divide the
uncompressed data into 64 KiB chunks and use a chunk offset array for
the compressed chunks to allow for quick random access without too much
overhead. The tradeoff is a limited possible compression ratio -- i.e.
we won't be as good as tar.gz (though surprisingly with my test
archives we did better than zip).

The other package file sections (package attributes and TOC) are no
longer compressed individually. Their uncompressed data are simply
pushed onto the heap where the usual compression strategy applies. To
simplify things the repository format has been changed in the same
manner although it doesn't otherwise use the heap, since it only stores
meta data.

Due to the data compression having been exposed in public and private
API, this change touches a lot of package kit using code, including
packagefs and the boot loader packagefs support. The latter two haven't
been tested yet. Moreover packagefs needs a new kind of cache so we
avoid re-reading the same heap chunk for two different data items it
contains.

packagefs: Add support for hpkg format V1

* Add union-like class PackageData which wraps the V1 and V2
BPackageData classes.
* GlobalFactory: Create a data reader depending on the data format
version.
* Package: Add a loader for V1 format and try that, if the other one
fails.

packagefs: PackageData: Fix copy and paste error

hpkg format: compress the whole heap

Instead of handling compression for individual file/attribute data we
do now compress the whole heap where they are stored. This
significantly improves compression ratios. We still divide the
uncompressed data into 64 KiB chunks and use a chunk offset array for
the compressed chunks to allow for quick random access without too much
overhead. The tradeoff is a limited possible compression ratio -- i.e.
we won't be as good as tar.gz (though surprisingly with my test
archives we did better than zip).

The other package file sections (package attributes and TOC) are no
longer compressed individually. Their uncompressed data are simply
pushed onto the heap where the usual compression strategy applies. To
simplify things the repository format has been changed in the same
manner although it doesn't otherwise use the heap, since it only stores
meta data.

Due to the data compression having been exposed in public and private
API, this change touches a lot of package kit using code, including
packagefs and the boot loader packagefs support. The latter two haven't
been tested yet. Moreover packagefs needs a new kind of cache so we
avoid re-reading the same heap chunk for two different data items it
contains.

packagefs: Add support for hpkg format V1

* Add union-like class PackageData which wraps the V1 and V2
BPackageData classes.
* GlobalFactory: Create a data reader depending on the data format
version.
* Package: Add a loader for V1 format and try that, if the other one
fails.