RFR: 8269131: Update libxml2 to version 2.9.12 [v2]

Tue Jul 6 18:32:56 UTC 2021

On Fri, 2 Jul 2021 11:30:30 GMT, Ambarish Rapte <arapte at openjdk.org> wrote:

>> We currently use libxml2 version 2.9.10. It should be updated to latest stable release, which is version 2.9.12.
>> The steps to update libxml are documented in UPDATING.txt.
>
> Ambarish Rapte has updated the pull request incrementally with one additional commit since the last revision:
> 
>   changes as per review

confirmed to work on linux, win, mac (x86_64)

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Marked as reviewed by jvos (Reviewer).

PR: https://git.openjdk.java.net/jfx/pull/562