desc. of non-standard hyphenation patterns in user-defined dict.

Change-Id: Ib202c5e1318b95b85f49b444ccfd511439a9c8c9
Reviewed-on: https://gerrit.libreoffice.org/7805
Reviewed-by: Andras Timar <andras.timar@collabora.com>
Tested-by: Andras Timar <andras.timar@collabora.com>