CIDs 1162783 & 1162784: out-of-bounds access & write in MSI.

* The number of IO vectors is not 256 on x86, but rather 224 as set by
  NUM_IO_VECTORS in "arch_int.h".
* Jessicah mentioned hearing about MSI crashes before, but that was a
  few weeks ago.
* These were the only CIDs in the MSI code.

Signed-off-by: Michael Lotz <mmlr@mlotz.ch>
package kit: PackageFileHeapReader::Init(): Sanity checks

Make sure the compressed/uncompressed heap size and the chunk size
table look plausible, so we can rely on the values later. Fixes
potential crashes for corrupt packages.
PackageWriterImpl: Move _Finish() impl to match order in header
BPackageWriter: Add Recompress()

Allows rewriting an existing package file with a different compression.
package: Add command recompress

The streaming feature for -0 is missing yet.