When alsactl saved state has dB level information and an attribute
of a control element is changed after save (e.g. volume range is
changed), try to restore the values to keep the same dB level.
This change requires the new alsa-lib functions for TLV dB
conversion, so we check it in configure (until AM_PATH_ALSA(1.0.16)
works).
Make "alsactl restore" a bit more robust. Now it tries to parse the
compound items in the case that the number of channels was changed.
The former mono-value is expanded to all channels.