* Add a new calcLoopNormals function to DerivedMesh struct, and implement it for CDDM and CCGDM (subsurf).
EditDerivedBMesh (edit mode DM) only gets a dummy one in this commit.
* Add a tessellated version of CD_LOOPNORMAL layer (CD_TESSLOOPNORMAL), with relevant code to handle it
(tessellation, rna access, etc.).
* Change auto_smooth options of Mesh (angle now in radian internaly, and toggle is now used to enable/disable
split normals in DM creation process). Note BI render code is not touched here, hence its behavior regarding
this option is now incoherent, will be addressed in a separate commit.
Reviewers: campbellbarton
CC: brecht
Differential Revision: https://developer.blender.org/D365
18e4224142