these reserved bits are supposed to be set to 0

(thanks Kieran!)
add MPEG audio parsing + complete ADTS
enhance mpga and adts support
support private stream 2 PES
add defines for audio type
add defines for stream types
new functions to detect sync header changes
do not compare mode extension
fix psi_get_version

Version is 5 bits instead of 4 bits, as reported by Sebastien (Coexsi).