SeaMonkey 2.53.4

What's new in this version:

SeaMonkey 2.53.4 contains (among other changes) the following major changes relative to SeaMonkey 2.53.3:
- Upgraded NSS to 3.53.1 bug 1643859
Updated to Unicode 11 for SpiderMonkey bug 1466471
Updated bundled Twemoji Mozilla font to v0.5.1 to support newer emojis bug 1644346
Updated how photos are handled in the addressbook bug 1641705
Removed outdated RSS feed handlers bug 1643716
Fix initialisation of TodayPane mini-day, to show the right day bug 1479628
Fixed sizing issue of HTML mail question (askSendFormat) dialog bug 1583415
Update of help page content and links
Various security and general platform fixes

SeaMonkey 2.53.4 contains (among other changes) the following major changes relative to SeaMonkey 2.49.5:
- The Bookmarks Manager has switched its name to Library, and now also includes the History list. When invoking History, the Library will be shown with the History list selected. The extensive modifications were needed because of Mozilla Gecko platform API changes.
- Download Manager has been migrated to a new API. Although it looks pretty much the same as before, the search option is missing and some other minor details work differently. The previous downloads history is removed during the upgrade.
- The layout panel was added to the CSS Grid tools.
- TLS 1.3 is the default SSL version now.
- The only NPAPI plugin which will work with SeaMonkey 2.53.4 is Flash. Support for other NPAPI plugins like Java and Silverlight has been removed. For displaying pdf files in the browser you can use pdf.js-seamonkey from Isaac Schemm.
- SeaMonkey now uses a new api for formatting regional data like time and date. Default is to use the application locale of the current SeaMonkey build. If you use a language pack or a different OS formatting this is usually not desired. You can change the formatting from the application locale to the regional settings locale (OS) in the preferences dialog under "Appearance".

Other:
- SeaMonkey 2.53.4 uses the same backend as Firefox and contains the relevant Firefox 60.6 security fixes.
- SeaMonkey 2.53.4 shares most parts of the mail and news code with Thunderbird. Please read the Thunderbird 60.0 release notes for specific changes and security fixes in this release.
- Additional important security fixes up to Current Firefox 78.1 ESR and a few enhancements have been backported. We will continue to enhance SeaMonkey security in subsequent 2.53.x beta and release versions as fast as we are able to.