Pass rgr structure through map functions

[czender]

Please modify your branch to pass the rgr structure through as deep as nco_sph_plg_area(). This is necessary to finish the next steps in the non-spherical triangle work. When that's done, please commit and push your latest so I can hook in the non-spherical work.

[hmb1]

@czender
I can do this but its really really really horrible !!
What about setting the "rgr" as a file static variable --check it all works and then i can do the horrible stuff ? What members of rgr do you need ?

[czender]

Just add this line to all the function protoypes down to nco_sph_plg_area():
(rgr_sct * const rgr, /* I/O [sct] Regridding structure */
It's the best way to expose all the regridding options to the routing that need them. I do not need any exisintg rgr members, I need to make available some new user-controlled flags to nco_sph_plg_area() and that is currently impossible.