For the most accurate detail, we recommend you review the git log
Minor release for slightly disruptive changes
Hotfix startup issues
Hotfix for a memory leak discovered in certain situations
Summary: the 3.3.1 release was slightly broken as the correct version number wasn't embedded in configure.in with undesirable effects for some people trying to build packages. The 3.3.5 release fixes that issue and returns to the autotools dist mechanism for consistency with prior releases. There is a mixed bag of minor bug fixes across almost all modules as summarised in the release notes.