The ClutterCanvas content implementation should be used instead, to
avoid stringing along the ClutterTexture API and implementation.
This change requires some minor surgery, as the deprecated section
already contains an header for the previously deprecated methods; plus,
we don't want to deprecate clutter_cairo_set_source_color(). This means
creating a new header to be used for Cairo-related API.
This also avoids the warning
Cogl-WARNING **: ./cogl-buffer.c:215: GL error (1285): Out of memory
generated by cogl_buffer_map when the CoglBuffer has zero length.
Both ClutterCanvas and ClutterImage should use the minification and
magnification filters set on the actor, just like the use the content
box and the paint opacity.
