Merge pull request protocolbuffers#7590 from haberman/merge-release-b…

…ranch

Merge release branch

Updated the changelog for the 3.12.2 release.

Added changelog entry for 3.12.1.

Added a changelog entry about the Java fix. (protocolbuffers#7516)

Updated Changelog for 3.12.0-rc2.

Added changelog entry for removing binary gems for Ruby <2.5. (protoc…

…olbuffers#7454)

Skip building distribution tar files for 32 bit Mac (protocolbuffers#…

…7214)

Changed the maven URL to use https when building dist artifacts

Fix Multiple Request for PHP (protocolbuffers#7008)

* Add scripts to test multirequest

* chmod ug+x multirequest.sh

* Add continuous test

* Compile c extension

* Class entry is obsolete in the second request
1) Needes to use class name in persistent map
2) Invalidate class entry stored in descriptor

* Add new files to dist

* Fix compile_extension

* Cleanup outputs for phpize

Add php 7.4 to docker image (protocolbuffers#6971) (protocolbuffers#6975

)

* Add php 7.4 to docker image

* Use https links