All dvbpsi decoders now use dvbpsi_t as handle instead of
dvbpsi_decoder_t *. The pointer to dvbpsi_decoder_t is privatized
and accessible through (dvbpsi_t *)->p_private member. The user
must make sure to cast it to the correct dvbpsi_*_decoder_t type
before accessing structure members.

Dvbpsi decoder developers should use the define DVBPSI_DECODER_COMMON
at the start of a new dvbpsi_*_decoder_t.

WARNING: THIS COMMIT BREAKS THE EXISTING API IN A MAJOR WAY !!!

- most public APIs requires a pointer to existing dvbpsi_t
- new functions to obtain and delete a pointer to dvbpsi_t structure:
  dvbpsi_NewHandle() and dvbpsi_DeleteHandle()
- subtable descriptors fixes
- indentations