Support for DIR-320/DIR-600 SquashFS about firmware-mod-kit HOT 4 CLOSED

Thank you for this contribution. I am going to add you as a contributor so that 
you can commit it yourself, and make any other changes you need to later (if 
any). Sound good to you? ;)

Done. Please let me know of any troubles. You should be able to close this 
ticket after you commit the changes.

Of course, as you know, the #1 rule is always be careful not to break 
compatibility with any other firmware types. I do not have an environment set 
up to automatically regression test every supported device, not to mention this 
would require actually flashing the built images to them to be 100% sure. 
Therefore, always be careful ;).

Your above patch is perfect, does what it needs, doesn't break anything. Great 
;)

Will tread with caution. :)

Patch applied and checked in. Thanks!

is it not necessary to add the 7zip strings to the squashfs filesystem when 
rebuilding the modified image? I ask because the router (wbr1310 revD) is not 
accepting my modified image and I haven't yet figured out why, but am trying to 
eliminate this as a possibility. I note the image built with fmk compresses 
better and pads the remaining blocks with 0xffff instead of 0x0000. I could 
probably figure out the code and send a patch, but won't bother if that's not 
likely the issue. thanks.