Squashfs now supports XZ and LZO compression in addition to ZLIB.
As such it no longer makes sense to always include ZLIB support.
In particular embedded systems may only use LZO or XZ compression, and
the ability to exclude ZLIB support will reduce kernel size.
Signed-off-by: NPhillip Lougher <phillip@squashfs.org.uk>

My existing email address may stop working in a month or two, so update
email to one that will continue working.
Signed-off-by: NPhillip Lougher <phillip@lougher.demon.co.uk>

Extend decompressor framework to handle compression options stored in
the filesystem.  These options can be used by the relevant decompressor
at initialisation time to over-ride defaults.

The presence of compression options in the filesystem is indicated by
the COMP_OPT filesystem flag.  If present the data is read from the
filesystem and passed to the decompressor init function.  The decompressor
init function signature has been extended to take this data.

Also update the init function signature in the glib, lzo and xz
decompressor wrappers.
Signed-off-by: NPhillip Lougher <phillip@lougher.demon.co.uk>

Get rid of messy repeated #if(n)def CONFIG_SQUASHFS_LZO code
in decompressor.c
Signed-off-by: NPhillip Lougher <phillip@lougher.demon.co.uk>

Move squashfs_i() definition out of squashfs.h, this eliminates
the need to #include squashfs_fs_i.h from numerous files.
Signed-off-by: NPhillip Lougher <phillip@lougher.demon.co.uk>

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

Signed-off-by: NChan Jeong <chan.jeong@lge.com>
Signed-off-by: NPhillip Lougher <phillip@lougher.demon.co.uk>

Add knowledge of lzma/lzo compression formats to the decompressor
framework.  For now these are added as unsupported.  Without
these entries lzma/lzo compressed filesystems will be flagged as
having unknown compression which is undesirable.
Signed-off-by: NPhillip Lougher <phillip@lougher.demon.co.uk>

This adds a decompressor framework which allows multiple compression
algorithms to be cleanly supported.

Also update zlib wrapper and other code to use the new framework.
Signed-off-by: NPhillip Lougher <phillip@lougher.demon.co.uk>