[email notifications] send notification at post-commit time (closes #2119248)

[devtools] Use Xvfb to run firefox in js tests on posix platforms This way we don't require running tests under X.

[i18n] fix pb with non-ascii chars in cwd. closes #2149063

[repository] add a ``gc_stats`` method and 2 more cache size for ``stats`` (closes #2179735) This method returns memory informations in a dictionnary (same informations as the content displayed by the GCView).