This commit includes lots of debug output and intended to save
current state for further tests. Minor changes include new time
calculation functions and the start of audio stream is synchronized with
the next nearest video frame (was between frames).

Audio samples are recorded after each frame which brakes the structure
of video chunks in case when frames_per_chunk > 1. This will be fixed
later.

Now, state->frame_lengths contains not only video frames lengths but audio
sample lengths as well if audio recording is enabled.

This commit also fixes a bug with 'exit' command processing

This commit fixes a bug introduced in 076161cd where a list of active
sensor ports is updated every time recording has started.

This commit starts to add audio recording to camogm. Basic code for ALSA
initialization and audio samples reading is added but recording to file
has not been implemented yet.

 Conflicts:
	src/camogm.c
	src/camogm.h

This commit also adds sensor port number to last_error_code returned in
xml status report.