Support OpenGL tessellation shaders

VTK now supports tessellation control and tessellation evaluation shaders in an OpenGL shader program. You can use the new enums vtkShader::TessControl and vtkShader::TessEvaluation to create shaders of type GL_TESS_CONTROL_SHADER and GL_TESS_EVALUATION_SHADER respectively.

The new overload of vtkShaderProgram::ReadyShaderProgram accepts source codes for tessellation control and evaluation shaders.

This feature is available starting from OpenGL version 4.1. You can use vtkShader::IsTessellationShaderSupported() to confirm whether the OpenGL driver supports tessellation shaders. For OpenGL 4.0 and lower, VTK automatically enables the GL_ARB_tessellation_shader extension while populating //VTK::System::Dec in shader code.