Prepare for a new Slovenian translation.
Add Slovenian translation (ticket #3643).
"Output" property page: Remove some dead code.
"Output" property page: "Shader" and "Rotation" were sometimes wrongly displayed as unavailable for "Sync renderer".

This commit fixes #3672.
Use UINT_MAX instead of -1 casted to UINT when the doc mentions 0xFFFFFFFF.