jffs2: Add lzma compression

Hello,
This patch adds Lzma support to mkfs.jffs2 using the 7z 4.58 ansi C
encoder/decoder. The compression optimization in a typical system was about 10% less than zlib. I've kept the original Lzma code intact so that it can be easily updated to latest versions of the lzma sdk. The lzma code worked perfectly well both in kernel and user space.

The compr_lzma.c attached is the file used by linux kernel to read data (only changes includes).

regards,
Nikos