Evas GL: Automatic fallback to indirect rendering when the scene has

Evas GL: Automatic fallback to indirect rendering when the scene has
not changed.

Automatically fallback to indirect rendering on FBO or X11 Pixmap
if the Evas Object Image is not marked as dirty. This should
improve the performance and/or power consumption in those
rare cases where this area of the canvas needs to be redrawn
but the GL content has not changed.

@feature