The next release (0.85) will most likely contain the feature you requested. As mentioned, flat shading will be emulated by feeding face normals into the gouraud shader instead of vertex normals, so it won't be any faster than gouraud.
In addition, it disables the usage of triangle strips, so it's even slower when using OpenGL support (not noticeable on nVidia hardware, quite noticeable on ATI cards).