RFR: 8262366: Update glib to version 2.66.7 [v2]

Sat Apr 3 07:20:16 UTC 2021

On Thu, 1 Apr 2021 23:17:58 GMT, Alexander Matveev <almatvee at openjdk.org> wrote:

>> - GLib was updated to version 2.66.7 and GStreamer to version 1.18.3
>>  - One bug was discovered in updated GStreamer which was causing deadlock or infinite loop during seek on macOS. See gstsystemclock.c for changes between ifdef GSTREAMER_LITE. Otherwise no changes.
>
> Alexander Matveev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Updated .md files and added missing include files

Marked as reviewed by jvos (Reviewer).

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PR: https://git.openjdk.java.net/jfx/pull/447