New yaffs2_image_maker tool to work with 4kB pages - still under test

This appears to be working but more testing required.

The tool now takes two new parameters for modifying the bytes per page
and pages per block.

For instance to create an inband tags image using 4kB virtual pages (ie. 32
virtual pages per block) try:

./yaffs2_image_maker -i test-dir2 -o outimage -w working_file -I -c 4096  -B 32

Signed-off-by: Charles Manning <cdhmanning@gmail.com>