Function gl::DrawElementsInstanced

pub unsafe fn DrawElementsInstanced(mode: GLenum,
                                    count: GLsizei,
                                    type_: GLenum,
                                    indices: *const c_void,
                                    instancecount: GLsizei)

Fallbacks: DrawElementsInstancedANGLE, DrawElementsInstancedARB, DrawElementsInstancedEXT, DrawElementsInstancedNV