This patch adds the option to set minimum/maximum latitude/longitude values for
the equirectangular panorama camera in Cycles, as discussed in T34400.
The separate functions in kernel_projection.h are needed because the regular
ones are also used as helper functions for environment map sampling.
Reviewers: #cycles, sergey
Reviewed By: #cycles, sergey
Subscribers: dingto, sergey, brecht
Differential Revision: https://developer.blender.org/D960
4118c1b4e6