WebKitGTK 2.51.2 released!

This is a development release leading toward 2.52 series.

Add WebKitImage utility class that will be used for favicons and snapshots.
Videos with BT2100-PQ colorspace are now tone-mapped to SDR, ensuring colours do not appear washed out.
Use a run loop observer also to notify the main thread when composition is done.
Remove the hybrid rendering mode now that we are computing a different tile size for GPU and CPU rendering modes.
Make jsc_value_array_buffer_get_data() introspectable.
Restrict allowed URI protocols for media playback.
Add rendering and buffer formats information to webkit://gpu.
Enable dynamic MSAA for accelerated 2D canvas rendering.
Fix several crashes and rendering issues.
Translation updates: Slovenian, Turkish.

Thanks to all the contributors who made possible this release.