compositor: implement inverse matrix transformation

compositor: implement inverse matrix transformation

Implement 4x4 matrix inversion based on LU-decomposition with partial
pivoting.

Instead of simply computing the inverse matrix explicitly, introduce the
type struct weston_inverse_matrix for storing the LU-decomposition and
the permutation from pivoting. Using doubles, this struct has greater
precision than struct weston_matrix.

If you need only few (less than 5, presumably) multiplications with the
inverse matrix, is it cheaper to use weston_inverse_matrix, and not
compute the inverse matrix explicitly into a weston_matrix.

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>