Check that CoreFoundation functions succeed

Several crash reports indicate failure to create a CFString (in ct::line_t’s constructor). As we have an explicit UTF-8 check, I am not sure why it would fail, but at least now TextMate should not crash when it happens.
Disable autoresize mask translation for divider line views
Add API to hide status bar
Introduce ‘hideStatusBar’ user defaults key
Store commit window frame in user defaults
fixup! Full implementation of ‘labels’ property