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.