openfimg: Work in progress (2013.12.30)

- Almost all of draw code already in place (missing cache invalidation
  and handling of constants).
- Implemented vertex buffer space allocation.
- Implemented buffer mapping.
- Added draw command emission.
- Added simple cache heuristics handling.
- Reworked and/or cleaned-up some code.

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>