isl_point_dim: use isl_point_peek_space
isl_point_dim: use isl_point_peek_space

This reduces the dependence on the internal representation.

Signed-off-by: Sven Verdoolaege <235c10dd23b819f81cdc9756a251746bc184cab6@gmail.com>

Meinersbur/isl,Meinersbur/isl,Meinersbur/isl,Meinersbur/isl