DocBuild
From Buzztard
[edit] gtkdoc
Problem:
- out of source build (e.g. at make distcehck) fails
- reason is that we use a version.entities file
- the file is generates in _build dir
- gtkdoc uses a hack to build in srcdir
- it cannot find the file
Solutions:
- fix gtkdoc
- copy the file also



