This patch changes the behavior of strictly bound textures such that
they are only updated if the corresponding window has been damaged.
Additionally GLTexture now keeps track of the current filter and
wrapmode setting.
REVIEW: 103655
Additionally:
- hide the GLTexture implementation using dpointers
- drop the unused function SceneOpenGL::Texture::optimizeBindDamage()
- Texture::load now loads a new texture and does not update the existing one
REVIEW: 101999
