Fix retrieving the shortname of autoloaded plugin functions
Fix video playback for very high speed factors

Also, slightly less broken playback on *nix
Allow Ctrl-A to select all on multiline wx.TextCtrl
Hide 'reset to default' control if the function was added by the user
Add 'open script's directory' menu option
Fix max digits allowed to be introduced on a crop editor's spin control
Fix creation of 'preview.avs' on Windows

os.access doesn't work properly for directories on Windows.  Replace
it with try/except.