Versioning Policy

The major version number names the overall API version. It is incremented on wide-ranged API changes. There is no downward compatibility guaranteed: The compatibility of the API is usually broken when this version number is incremented.
The minor version number is incremeted on API changes that might break downward compatibility, but only locally, so that only a few tweaks are neccessary (if any) in order to upgrade.
The patch version number is incremeted on such changes that neither of the two prior rules apply to: Full downward compatibility is guaranteed both on API and ABI level, thus one should always try to use the most recent patch version.

Changelog