TODO

(in abitrary order)
- pdf generation
  - alpha channel support
  - support for more drawing modes (XOR, AND, OR, alpha, blend)
  - text attributes
  - check: char spacing
  - security settings (printing, copying, changing, ...) -> not with PDFlib :(
  - password protection (ditto)
  - thumbnails? note recent Acrobat Reader doesn't require them; BePDF does not support them.
  - optimize CID tables; the mapping from Unicode to CID is not required, it is sufficient
    to know whether a code point is in a certain CID table or not! -> use bitfield instead

