v2.6.7 - Fixes for double free bug #546, changes to release process

[Kyle]

This release contains a fix for bug #547. Hopefully. It is a Heisenbug that is difficult to trigger consistently.  There is now a test in place that was able to repro it.

Thanks to user "2gd4who" from the forum who noticed this.

There are also a lot of changes to how the releases are done. I broke up the ZIP files that had contained everything for each target before. Now each target has three ZIP files (example shown for macOS on ARM64):

• libplctag_2.6.7_macos_aarch64.zip - everything as before
• libplctag_2.6.7_macos_aarch64_tools.zip - the basic library and files needed to develop with libplctag plus tools like tag_rw2, tag listing tools etc.
• libplctag_2.6.7_macos_aarch64_dev.zip - just the files needed to develop with libplctag.

The last two are experimental. Let me know if there is a flaw with them.

The final change is more automation around releases. This should help me get them out the door more easily and more frequently. Now when a PR is merged to the release branch, it automatically creates a release and tags it.

Best,

Kyle