In revision 1512 I merged a change which fixes a translation bug. Some
of you may have noticed, that buttons ("OK", "Cancel", ...) and menu
entries ("Copy", "Paste", ...) were not translated. To make it short:
The translation files for default strings are provided by Qt and not by
us. (The files are named qt_<lang>.qm).
Now the important part for the windows and OSX builds:
The /qt_<lang>.qm/ (e. g. /qt_es.qm/) files have to be included in the
build and copied to the folder where our own translations are copied
Please document required changes in the wiki  and change the build
scripts in our code base.
If you have any question in regard to this, please ask.