Open C API interface to the routines to subdivide a face using an isocline method.

The subdiv functions provide routines that subdiv features. The subdiv feature
splits a face using an isocline method. These functions enable you to:
. Obtain the parameters used for a subdiv feature.
. Obtain the type of subdiv feature.
. Create a subdiv feature
. Edit a subdiv feature.
. Free space allocated by UF_SUBDIV_ask_parms.