WebKitGTK+ 2.8.3 release.

Compared to the previous 2.8.1 build in Fedora 22, the changes include:

What's new in the WebKitGTK+ 2.8.2 release?

• Fix network redirection to a non HTTP destination.
• Use a webkit subdirectory for the disk cache to avoid conflicts with other files in the cache directory when the disk cache is cleaned up.
• Do not preserve the Origin header on on cross-origin redirects.
• Prevent WorkQueue objects from being leaked and ensure its worker thread always exits.

What's new in the WebKitGTK+ 2.8.3 release?

• Fixed a regression introduced in 2.8.2 that broke downloads when using the network process.
• Fix the build with Netscape plugins disabled.
• Fix XPixamps leaked by GLContext when using EGL on X11.