libbuxton: Handle CHANGED in response_value
libbuxton: Handle CHANGED in response_value

Clients may now use response_value(response) to obtain the value
when they recieve a notification for a key change.

Signed-off-by: Michael Ikey Doherty <15e2f59c60e9d84348e78a87e24660774f739add@intel.com>

sofar/buxton,sofar/buxton