[Libreoffice] [REVIEW][3-5] looking for .mozilla/.thunderbird under .config dir

[Caolán McNamara]

As julien points out, we're using osl::Security::getConfigDir to find
the right dir to look for ".mozilla" and ".thunderbird" etc underneath.
getConfigDir uses XDG_CONFIG_DIR thesedays, but moz never did that, so I
reckon we should cherry-pick
http://cgit.freedesktop.org/libreoffice/core/commit/?id=6be6357cce999e5a1a692da1f682847be3723587
to 3-5

C.