Tidy up the 004/005 processor a bit.

Introduce methods for handling individual bits, instead of having
a pair of giant if statements of doom.

Tidy some comments and formatting up at the same time.

This is functionally the same as it was before.

Change-Id: I83f09cb6c36be203d102c44188f90de2b0587e58
Reviewed-on: http://gerrit.dmdirc.com/2812
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <greg@dmdirc.com>