Fix build with current qtdeclarative.

Change-Id: I1315d984216309ed2f76e8326c231752aa98ab3e
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Performance enhancements for map tile textures

Unnecessary image conversion for premultiplied textures is now avoided.

Map tile textures are now applied correcly to their geometries, so that
vertical mirroring is no longer needed for the textures.

Mipmaps are disabled for map tile textures. Different tiles are already
used for different zoom levels.

Change-Id: I546bffc8b7f6b2a777d9805c434697f2284ec082
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>