qtmux: support more of j2k

qtmux: support more of j2k

Reads the new caps added to qtdemux by commit
c917d65e6df0b5d585f905c7ad78a8a0a44b2cb0
and adds its corresponding atoms.

Also adds support for image/x-jpc as it is the same
as image/x-jp2, except that the buffers need to be
boxed inside a jp2c isom box before muxing. To solve
this the QTPads now have a function that (if
not NULL) is called when a buffer is collected. This
function returns a replacement to the current collected
buffer.

Fixes #598916