Should still be sufficient for ERP5 unit tests: largest test uses 3 DB, and
we want to run 10 tests in parallel.

Buildout output is less scary this way.

Explain custom configuration files.

Avoid Nonetype-related errors.

TODO: Would be better to sanitize every parameter at beginning.

because the output seems broken with enabling thread safe.

(librsvg 2.37 requires newer pango.)

* enable thread safe
* build without libidn