_cairo_surface_create_in_error(): Add PNG_ERROR support

Traditionally, loading a malformed PNG file with cairo_image_surface_create_from_png() resulted in CAIRO_STATUS_NO_MEMORY. This was apparently changed in commit c5ee3f11 by adding CAIRO_STATUS_PNG_ERROR and using it for errors returned from libpng. However, I don't see how this was supposed to actually work.

There are a couple of error codes supported by _cairo_surface_create_in_error(). Anything else is turned into CAIRO_STATUS_NO_MEMORY, which is not a helpful status. For this reason, CAIRO_STATUS_PNG_ERROR would be turned into CAIRO_STATUS_NO_MEMORY.

This commit adds support for CAIRO_STATUS_PNG_ERROR to _cairo_surface_create_in_error() so that this error can actually be returned to the caller.

Signed-off-by: Uli Schlachter psychon@znc.in