With certain malformed jpegs the call to jpeg_finish_decompress
caused a long jump back to stop_loading. This jump overwrote the
value of the surface pointer which should be NULL which in turn 
caused a cairo assert when trying to get a reference to a surface
with ref_count = 0.

Also moved the cleanup of in_buffer out of the !finished scope, 
as it seems this would otherwise be a potential leak.

The cairo surface could have the width and height swapped
compared to the original image if the image orientation is
rotated.

Iterate over the cairo surface dimensions instead of the
original dimensions when copying the pixels into the cairo
surface.

do not call siglongjmp more then once in case of error

ignore the error if the surface is not null

[bug #795879]

this makes color profiles work on wayland as well.

use a better filter to scale the image

added other points where the cancellable is checked

to avoid possible out-of-memory errors.

similar to  cairo_image_surface_create but returns NULL on error.

initialize the tables inside a mutex lock

and use it instead of _cairo_image_curface_scale_to that uses the cairo
bilinear filter.

surround code that changes the surface data directly with calls
to flush and mark_dirty.