Use `exec` for running java.

This replaces the shell process, which is no longer needed, by the
java process.
Updating to Freeplane release 1.2.23.
Fix and enhance a comment.
Fix: Version of tar-file has a sub-version postfix.
Update 40_no_winmac.patch for current version of build.xml.
Remove useless build-patches: we use a different build target.

These two pathces are related to the build target `dist`, but we are
building the target `build`, which does not include `dist`. So these
patches are unnecessary.
Update changelog in .spec-file.