bob is alive in the kernel

Implement bob walker as a linux character device driver such that one may `cat` bob's device file to glean his thought leadering.

Possibly even more performant than @samjsharpe's user-space C implementation ;-) Though clearly not as accomplished as the Perl version.

Apologies to bob for this not being a Solaris module.

Rather limited in terms of modes it supports currently, though I wonder if we can't use the Linux boot loader flags to set sport mode etc.

Also doesn't accept any writes as yet and requires the user to run `mknod`, which should be avoidable using `udev` and `device_create()`.
I've removed the `vmalloc` so `vfree` is probably unnecessary now.