* HCSBB could cause an issue for regular cells that has two of its vertices at a pole. The triangulation would cae on of the two triangle to be a single line, which was not correctly handled.

now takes areas differences between edges following circles of constant latitude and edges following great circles into account during barycenter computation

* some reordering of operations
* improved documentation

* rbf can also be added to an interpolation stack configuration via the NNN routine

* thanks to Andrea for the hint

* in dark mode contents of latex generated formulas would be basically invisible

* this should espectially work well on vector machines
* it is enabled by compiling with "-DYAC_NEC_EXPERIMENTAL"