The function dvbpsi_DetachDemux(), which is now a wrapper around dvbpsi_chain_demux_delete()
failed to check the return value. Now it returns an error message when the return value is 'false'.

Dereference after NULL check (Fixes CID #134926, #134927, #134928, #13429, #13430, #134931, #134932, #134933, #134934, #134935, #134936, #134937, #134938, #134939, #134940)

Check the dvbpsi handle before passing it to dvbpsi_chain_demux_delete().

(cherry picked from commit cad97408)
Signed-off-by: Jean-Paul Saman <jpsaman@videolan.org>

All decoders implemented a new property named p_cb_data. This patch
moves the usage to dvbpsi_decoder_t::p_priv. The callback data is now
a dvbpsi decoder generic property.

By removing the i_program_number argument from dvbpsi_pmt_attach() its prototype then
matches that of all other dvbpsi_*_attach() functions. The i_extension was already used
as being the program number in case of PMT tables since the beginning of libdvbpsi its
implementation.

Treat i_program_number as i_extension.

If a dvbpsi_t handle was created but the attached PSI table demuxer was
never triggered because the table is not present in the stream, then the
function dvbpsi_chain_demux_delete() would not free its resources properly.
This caused dvbpsi_delete() on the dvbpsi_t handle to fail.

The function dvbpsi_chain_demux_delete() is changed to handle this situation
properly.

PMT are attached by using dvbpsi_pmt_attach() function directly and not through
a demuxing chain, so release the PMT's in the same manner. Thus using the
function dvbpsi_pmt_detach() directly.

It is the responsibility of the calling application to release dvbpsi_decoder_t::p_priv pointer
and its associated memory.

The function is replaced by dvbpsi_decoder_chain_get() that looksup a
decoder by its table_id and extension in a linked list.

Only when dvbpsi_decoder_t::pf_del() is not available dvbpsi_decoder_delete() is called
from this function.

This example application has been superseeded by dvbinfo example.

Directly accessing dvbpsi_t::p_decoder is no longer safe, since this holds
a linked list (aka chain) of decoders now.