[patch] Add a encryption key parameter to the compress / decompressfunction.

[Joel Reardon]

Compress and decompress now have an extra u8 *key field, and NULL is
passed wherever it is used. Later this will be used for an encryption key
for the data being compressed/decompressed (and NULL if no cryptographic operations should be done.)

Signed-off-by: Joel Reardon <reardonj@xxxxxxxxxxx>