Add headers_test.sh. A script that checks if every biTStream header
can be used standalone (includes all needed headers to implement
its functionality).

Add support for tdt_print() and examples/dvb_print_si support.

- Set reserved bits to 1 in cat_init().
- Add cat_set_desclength()
- Add support for CAT in examples/dvb_print_si.

Inspired by XML descriptor printer that already does the same.

Use definitions from table 100 of EN 300 468.

Setting of teletext_type and teletext_magazine was 1 bit off, instead
of bits 5/3, bits 6/2 were used.

Add missing desc5f_set_specifier() function and also print the specifier
as hex.

Add missing init and set functions and also fix printing.