Release v0.23 and v0.22.3

[carlosmn]

It's about time we release the next libgit2, and the last maintenance release of the current one. I would like the submodule changes to make it in as that's one the last pieces of API which I know we would have to change before long-term support.

This release should be one of the last before we agree on long-term support for the existing API and release 1.0.

For v0.23

• See what PRs we want to merge
• Check to see if there's anything missing in CHANGELOG
• Choose a codename "Entschuldigung"
• Bump the SOVERSION
• Bump the version string and defines
• Update the 101 examples
• Check for leaks
• Create the maint branch

For v0.22.3 ✔️

• See which fixes are worth backporting from master
• Bump the version string and defines

[b35li]

When the release will be made?

[carlosmn]

Soon, hopefully. I plan to make the maintenance release today. v0.23 still needs some work.

[carlosmn]

libgit2 v0.22.3 is out now, to be followed hopefully this week by the first rc for v0.23.

[carlosmn]

The examples have a PR to update them, libgit2/libgit2.github.io#54