Fritz!Box exploit: Added Big Endianess, improved check()-Function

Some Fritz!Box devices also run in Big Endianess mode (e.g. Version 7360). 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.

Furthermore, it's possible to send 92 bytes.