The DiffIterate call accepts a data structure argument containing the
parameters of the image to "diff" and a callback function. This callback
is called in the C code, making use of the recently added callbacks
helper.
The callback itself is called with the offset and length of the
differing area in the image as well as a data parameter so that
a common function can distinguish or update different data for
different calls if needed (compare to a void* in C).
Signed-off-by: John Mulligan <jmulligan@redhat.com>
