Version 8.0.0 beta 4

IECore

• Optimised polygonNormal and polygonWinding in PolygonAlgo.h.
• Added face normals mode to MeshNormalsOp.

IECoreGL

• Fixed shading of polygon meshes with no "N" primitive variable (#118).

IECoreArnold

• Added support for Arnold parameters of type AI_TYPE_BYTE.
• Added compatibility with Arnold 4.1.
• Fixed hangs in procedurals.