Add sbox_deg() function -- not necessary!

[esabol]

Awhile back, the spoint_deg(), scircle_deg(), sploy_deg() functions were added for convenience with arguments in degrees (instead of radians), but sbox_deg() was not added at the time. We have a use-case for it, so I would like to add it.

[esabol]

Oh, never mind. I should have looked at the source code first. sbox() takes spoints as arguments, not float8s, so this is unnecessary.