In preparation for more flags (not all of the backend dfa based),
rework the optimization and dump flag handling which has been exclusively
around the dfa up to this point.

- split dfa control and dump flags into separate fields. This gives more
  room for new flags in the existing DFA set
- rename DFA_DUMP, and DFA_CONTROL to CONTROL_DFA and DUMP_DFA as
  this will provide more uniform naming for none dfa flags
- group dump and control flags into a structure so they can be passed
  together.

Signed-off-by: John Johansen <john.johansen@canonical.com>