Log Message:
Update to 0.15.8:

0.15.8:
- Phase three of the refactoring [Søren Sandmann Pedersen]
- Fixes for refactoring fallout [Jonathan Morton, Jeff Muizelaar,
     Luca Barbato, Magnus Kessler]
- Improved testing code [Siarhei Siamashka]

0.15.6:
Apart from a few bug fixes, this release contains phase two of the
refactoring; in this phase the various types of images are split
into their own files.

0.15.4:
A new pixman release 0.15.4 is now available. This is a development
release leading up to a stable 0.16.0 release. News:

        - New ARM NEON fast paths [Ian Rickards, Jeff Muizelaar]

        - The first part of a large refactoring of the pixman code
          base [Søren Sandmann]

        - Bug fixes [Adam Jackson, Alan Coopersmith, Siarhei
          Siamashka, Jonathan Morton]