[cairo] iccompose.c/fbccompose.c merge part 2

[Billy Biggs]

Carl Worth (cworth at cworth.org):

> In other words, I don't want to see any libpixman commits that cause
> cairo/test failures. If the functional changes can be validated as
> "good" then the reference images should be updated in concert with the
> patch.
> 
> Basically, this merge of the xserver code into libpixman gives us a
> nice opportunity to carefully look at each change with the help of at
> least some test suite, and I don't want to miss that opportunity.

  I was just looking for more help with narrowing down the failures.

  -Billy