Framebuffer: call glDrawBuffers automatically.
To render into a Framebuffer with multiple color attachments, something like
static GLenum buffers[] = {GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1};
glDrawBuffers(2, buffers);
has to be called while the Framebuffer is bound. It would be desirable to do this automatically when multiple textures are attached to a Framebuffer.