This patch adds Canon Powershot driver (tested on Powershot A520) and fixes problems with cameracompress driver that I met while testing powershot driver.
This driver uses recently added features of camera interface. It fully supports Powershot cameras, I mean, fully, with flash on/off and live image capture (sic!) - before I wrote it, I didn't know this camera is capaple for that! This is the main reason you had to wait for it for so long.