Refactoring of encode loop and bitstream packing

Some code re-factored / moved to allow the main
pack operation inside the recode loop so  that the
size estimate is accurate.

Deletion of some redundant code relating to one pass.

Aproximate improvement over March 27 code base:
Derf 0.0%, YT 0.5%, YThd 0.3% Std_hd 0.25%

Change-Id: Id2d071794ab44f0b52935f6fcdb5733d09a6bb86