Use libjasper instead of relying on the external jasper program.

From the original ReviewBoard description:

I saw that for yahoo - webcam images are converted by running an
external program. Personally I am not ok with this since running an
external program every 0.X seconds is a bit expensive. Also, not to
mention using disk files (at least pushing directly into the program
and reading its output would have been better).

Also - I saw that inviteWebcam action was checking for presence of
jasper program - but requestWebcam should also have done that. Not
to mention that if a yahoo contact just invites you to see his cam,
you might get a feedback of missing program after accepting to
invitation. Not necessarily a big deal, though.

Original patch by Cristi Posoiu <cristi.posoiu AT gmail>, thanks!

This commit is a forward-port of r1217895 to the 4.6 branch.

REVIEW: 6312