CRC update failed - Netis WR2419 firmware

```
What steps will reproduce the problem?
1. extract firmware
http://www.netis-systems.com/Files/others/WF2419/netis(WF2419_WF2419D)-V1.2.2943
3.zip
2. make some changes (in web for example)
3. build firmware

What is the expected output? What do you see instead?
Firmware which i could upload to device. If i try, device firmware do not
accept (Bad CRC? or some magic number?)

# ./build-firmware.sh
Firmware Mod Kit (build) 0.99, (c)2011-2013 Craig Heffner, Jeremy Collake

Preparing tools ...
Building new squashfs file system... (this may take several minutes!)
Squahfs block size is 64 Kb
Creating big endian 2.1 filesystem on
/home/makr/vyvoj/fmk/fmk/new-filesystem.squashfs, block size 65536.

Big endian filesystem, data block size 65536, compressed data, compressed
metadata, compressed fragments
Filesystem size 2030.12 Kbytes (1.98 Mbytes)
30.42% of uncompressed filesystem size (6673.26 Kbytes)
Inode table size 2699 bytes (2.64 Kbytes)
30.11% of uncompressed inode table size (8963 bytes)
Directory table size 3101 bytes (3.03 Kbytes)
59.90% of uncompressed directory table size (5177 bytes)
Number of duplicate files found 3
Number of inodes 412
Number of files 264
Number of fragments 28
Number of symbolic links 104
Number of device nodes 23
Number of fifo nodes 0
Number of socket nodes 0
Number of directories 21
Number of uids 1
root (0)
Number of gids 0
Remaining free bytes in firmware image: 24546
Processing 0 header(s) from /home/makr/vyvoj/fmk/fmk/new-firmware.bin...
New firmware image has been saved to: /home/makr/vyvoj/fmk/fmk/new-firmware.bin

What version of the product are you using? On what operating system?
0.99 . Debian wheezy

Please provide any additional information below.
I think the problem is, that script do not know firmware structure. It detect
the data, but not all i think

```

Original issue reported on code.google.com by `martin.m...@gmail.com` on 21 Jul 2015 at 4:37

Start by rerunning build-firmware.sh with the Netis WF2419 firmware and inspect the generated new-firmware.bin alongside the original image. Trace how the script detects and processes headers, then verify completion by producing an image the device accepts without a CRC or magic-number error.

Written by the indexing model from the issue text.