mesh.Specular - Minor Change

mesh.Specular - Added: Require `VERTEX_SPECULAR` flag in C++ code of shader.

mesh.Specular - Mesh.Specular works. It's used in Lightmapped_4WayBlend.

mesh.Specular - Added clarification about the COLOR1 semantic. + Added NOTE about this function not working. + Added comparison with mesh.Color function.

mesh.Specular - Minor Change

mesh.Specular - No change reason was given