gdk-pixbuf 2.36.2 release.

* Remove the pixdata loader (#776004)
* Fix integer overflows in the jpeg loader (#775218)
* Add an external thumbnailer for images
* Fix a NULL pointer dereference (#776026)
* Fix a memory leak (#776020)
* Support bmp headers with bitmask (#766890)
* Add tests for scaling (#80925)
* Handle compressed pixdata in resources (#776105)
* Avoid a buffer overrun in the qtif loader ($#775648)
* Fix a crash in the bmp loader (#775242)
* Fix crash opening pnm images with large dimensions (#775232)
* Prevent buffer overflow in the pixdata loader (#775693)
* Translation updates