Support multiple tangents for BI render & viewport

Normal Map node support for GLSL mode and the internal render (multiple tangents support).

The Normal Map node is a useful node which is present in the Cycles render.
It makes it possible to use normal mapping without additional material node in a node tree.
This patch implements Normal Map node for GLSL mode and the internal render.

Previously only the active UV layer was used to calculate tangents.

release/scripts/startup/nodeitems_builtins.py

@@ -160,6 +160,7 @@ shader_node_categories = [
         NodeItem("ShaderNodeMapping"),
         NodeItem("ShaderNodeVectorCurve"),
         NodeItem("ShaderNodeVectorTransform"),
+        NodeItem("ShaderNodeNormalMap"),
         ]),
     ShaderOldNodeCategory("SH_CONVERTOR", "Converter", items=[
         NodeItem("ShaderNodeValToRGB"),