Fix a memory leak when opening the Properties > Clip page.
Fix a memory leak when drawing the chapter marks on the seek bar.

Since the seek bar is often redrawn the memory leak could become quite noticeable if a file was left opened for a long time.
Portuguese translation: remove year from About dialog.
Update Greek translation.
Update Ukrainian translation.

* Move link from About page to Authors.txt.
* Remove unneeded newline.
Swedish translation: add missing period in About dialog.
Update Simplified Chinese translation.