ftmod_pritap: Hexdump I/O buffers if q921_raw debug is enabled, improve parse_debug()

Add support for "q921_all"/"q931_all" to parse_debug() ("debug" span parameter), taken from
ftmod_libpri.

Passive libpri's raw dump feature is broken (e.g. I-frames missing), so
add "q921_raw" hexdump support to the pritap I/O read/write function.

Signed-off-by: Stefan Knoblich <stkn@openisdn.net>
ftmod_pritap: Use strcmp() for "none" and "all" in parse_debug()

Signed-off-by: Stefan Knoblich <stkn@openisdn.net>
FS-5009