Move zlib buffer init/destroy code into separate wrapper file.  Also
make zlib z_stream field a void * removing the need to include zlib.h
for most files.

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>

Squashfs is broken on any system where the page size is larger than
the metadata size (8192).  This is easily fixed by ensuring cache->pages
is always > 0.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Doug Chapman <doug.chapman@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>

This fixes a code regression caused by the recent mainlining changes.
The recent code changes call zlib_inflate repeatedly, decompressing into
separate 4K buffers, this code didn't check for the possibility that
zlib_inflate might ask for too many buffers when decompressing corrupted
data.

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>