cff.cpp: Miscellaneous clean up
cff.cpp: Miscellaneous clean up

* Replace a few literal numbers with sizeof(...); there are still
  a lot of numbers that should be replaced.
* Change buffer allocation for module loading: allocate only
  header.size plus padding and swap buffers for packed files.
  Check for minimum module size before accessing data.
* Reorder some blocks/statements to clarify or simplify things,
  merge identical code, or eliminate branches.
* Simplify event pointer address calculation for track conversion
  by introducing a pointer to multi-dimensional array variable.
* Initialize and update track counter in for loops headers.
* Merge adjacent string literals.
* Shrink scope of variable definitions.
* Replace malloc/free with new/delete, use memcpy instead of open
  coded copy, drop unneccessary memset or use initialization instead.
* Use a switch statement in cff_unpacker::unpack(). Differentiate
  between success and failure by using different labels when jumping
  out of the surrounding loop.
* Remove dead stores to old_code. It's no longer used at all.
* Eliminate superfluous temporary string and double copy from
  cff_unpacker::translate_code().
* Spacing, line breaks, and indentation changes.
* Update a few comments.

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