WebKitGTK+ 2.20.3 released!

This is a bug fix release in the stable 2.20 series.

Fix installation directory of API documentation.
Disable Gigacage if mmap fails to allocate in Linux.
Add user agent quirk for paypal website.
Properly detect compiler flags, needed libs, and fallbacks for usage of 64-bit atomic operations.
Fix a network process crash when trying to get cookies of about:blank page.
Fix UI process crash when closing the window under Wayland.
Fix several crashes and rendering issues.
Security fixes: CVE-2018-4190, CVE-2018-4199, CVE-2018-4218, CVE-2018-4222, CVE-2018-4232, CVE-2018-4233, CVE-2018-4246, CVE-2018-11646.

Thanks to all the contributors who made possible this release.