Merge https://github.com/j6t/gitk

* 'master' of https://github.com/j6t/gitk: gitk: offer "Copy commit ID to X11 selection" only on X11 gitk: support auto-copy comit ID to primary clipboard gitk: prefs dialog: refine Auto-select UI gitk: UI text: change "SHA1 ID" to "Commit ID" gitk: add text wrapping preferences gitk: make headings of preferences bold gitk: check main window visibility before waiting for it to show gitk: sv.po: Update Swedish translation (323t)