
* doc: explain how to exploit symmetry in certain structures

* Add support for z-directed PMLs.

* doc: explain -5 option

* verify correct functioning of PMLs and waveguide curvature in scalar
  mode

* mgp.c: some primitives may be intersected more than once by a given
  line. this is not handled properly at the moment.

* add single-precision calculations (can save memory)

* Make pseudo-2d mode work again.

* The rough polarization guessing could be extended to handle
  correctly the case of inhomogeneous grids.
