Bx component for prism fails in point on vertices
Bx component for prism fails in point on vertices

There is a singularity in the formula if the computation point is
aligned with one of the vertices of the prism. The test now uses a grid
that has points that coincide with the prism edges so that it catches
this kind of error.

santis19/fatiando,fatiando/fatiando,eusoubrasileiro/fatiando,mtb-za/fatiando,victortxa/fatiando,eusoubrasileiro/fatiando_seismic,victortxa/fatiando,fatiando/fatiando,eusoubrasileiro/fatiando,rafaelmds/fatiando,cmeessen/fatiando,drandykass/fatiando,eusoubrasileiro/fatiando_seismic,mtb-za/fatiando,santis19/fatiando,drandykass/fatiando,eusoubrasileiro/fatiando,cmeessen/fatiando,rafaelmds/fatiando