snapshot-21

Find menus, preferences, accessibility

- The macvim color scheme changed so that line numbers look better when
  the background is dark (enable line numbers with :set number, set dark
  background with :set bg=dark)
- Improved support for Voice Over (enable with <D-F5>)
- System bell support (see :h 'vb' on how to turn it off)
- MacVim no longer associates to .plist and .dict since these may well
  be in binary format
- Added Find Next <D-g>, Find Previous <D-G> and Use Selection for Find
  <D-e> menu items
- Track pad scrolling is now force sensitive
- Added help section on preferences
- Preferences panel updated (also no longer hides when MacVim loses
  focus)