Added Big Endianess, improved check()-Function

Some Fritz!Box devices also run in Big Endianess mode. However, since
"uname -a" always returns "mips" and the "file"-command is not
available, autodetection is not an easy task.

The check()-function now checks, whether the device is really
vulnerable.

Furthemore, it's possible to send 92 bytes.
Do final / minor cleanup
Align things
Land #3207, @7a69 MIPS BE support for Fritz Box's exploit