WebKitGTK 2.51.1 released!

This is the first development release leading toward 2.52 series.

Use the GPU process for WebGL by default.
Add initial API for web extensions.
Add API to handle WebXR permission requests.
Add new API to query the immersive session status.
Improve text rendering performance
Compute the layers tile size, using a different strategy depending on whether GPU rendering is enabled.
Add support for run loop observers that are now used to replace the layer flush timer and properly implement the opportunistic task scheduler.
Fix rendering fo gradients with hue interpolation method.
Fix rendering of layers with fractional transforms.
Fix pasting image data (like image/png) from the clipboard.
Remove support for building with libsoup2.
Fix several crashes and rendering issues.
Translation updates: Bulgarian, Slovenian, Swedish.

Thanks to all the contributors who made possible this release.