OpenGL: stipple support added to basic GLSL shader

The is intended to replace the deprecated glPolygonStipple() calls with a shader
based alternative, once we switch over to GLSL shaders.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D1688

source/gameengine/Rasterizer/RAS_OpenGLRasterizer/RAS_OpenGLRasterizer.cpp

@@ -553,6 +553,8 @@ void RAS_OpenGLRasterizer::SetEye(const StereoEye eye)
 			break;
 		case RAS_STEREO_VINTERLACE:
 		{
+			// OpenGL stippling is deprecated, it is no longer possible to affect all shaders
+			// this way, offscreen rendering and then compositing may be the better solution
 			glEnable(GL_POLYGON_STIPPLE);
 			glPolygonStipple((const GLubyte*) ((m_curreye == RAS_STEREO_LEFTEYE) ? left_eye_vinterlace_mask : right_eye_vinterlace_mask));
 			if (m_curreye == RAS_STEREO_RIGHTEYE)