Enable basic AppleScript support

Putting this key into the Info.plist file turns on the basic AppleScript
support Cocoa provides.  Doing so allows MacVim to receive some basic
events.  This gives MacVim a bit better integration into Mac OS X.

Below is an example which, when placed in one's .vimrc file,  causes the
window to be zoomed during startup.

let script='osascript -e "tell application \"MacVim\""'
       \ . ' -e "set zoomed of first window to true"'
       \ . ' -e "end tell"'
au VIMEnter * call system(script)

src/MacVim/Info.plist

@@ -617,6 +617,8 @@
 	</array>
 	<key>SUFeedURL</key>
 	<string>http://bjorn.winckler.googlepages.com/macvim_latest.xml</string>
+	<key>NSAppleScriptEnabled</key>
+	<true/>
 	<key>UTExportedTypeDeclarations</key>
 	<array>
 		<dict>