WITHOUT_BZIP2?

hello,

src.conf(5) documents the WITHOUT_BZIP2 knob.   however, unless i'm
missing something, this knob doesn't actually do anything, i.e. it
has no effect on the built system.

we could fix this in two ways:

- actually implement the option, to not build bzip2(1), libz2, etc.

- remove the option.

i am inclined towards the second option, since no one has complained
about the option not working, and therefore almost certainly isn't
using it.