adjust log level
improve PAT/PMT parsing

more compliant with the spec
partial merge from https://github.com/r0ro/HLSprovider/commit/a881bdce2fa7f820e1ad87d6f400b16711963cec
prepare for multiple audio track support
all testing streams are still working fine after this change
support multiple audio tracks in MPEG2-TS container

inspired by @r0ro commit : https://github.com/r0ro/HLSprovider/commit/a881bdce2fa7f820e1ad87d6f400b16711963cec
add an API for dynamic audio track switching
all test streams are working fine after this change
fix https://github.com/mangui/HLSprovider/issues/77