The names for channels provided by <sys/soundcard.h> have a padding with
space when their name is shorter than 6 characters, and this cause
excluding them difficult.
The new comparison code makes sure this padding is properly handled during
the match search.
Took the opportunity to bring light changes to try to improve the
readability of the channel listing code.
Signed-off-by: Christophe CURIS <christophe.curis@free.fr>