Fix T37225: UV map for closed curves incorrectly generated

Fix T37225: UV map for closed curves incorrectly generated

Summary:
Curve ORCO was not calculating properly for cyclic 2D curves.

- Needed to split vertices for blender internal renderer.
  Otherwise it's not possible to map last face to a proper
  texture location.

- Needed to tweak curve->mesh conversion to respect cyclic
  flag along U direction.

- Removed check for orcodm in curve.c:add_orco_dm since
  this code is only called if there're enabled constructive
  modifiers on the curve.

Reviewers: brecht

Maniphest Tasks: T37225

Differential Revision: http://developer.blender.org/D45