Cleanup: Extract code to launch a Mac WebKit application into a common function

Cleanup: Extract code to launch a Mac WebKit application into a common function
https://bugs.webkit.org/show_bug.cgi?id=68662

Reviewed by Adam Roben.

Extracts common code to launch a WebKit application on Mac OS X into a function
so that we can remove duplicate code.

* Scripts/run-webkit-app: Modified to use webkitdirs::runMacWebKitApp().
* Scripts/webkitdirs.pm: Sorted @EXPORT list and added constant USE_OPEN_COMMAND.
(runMacWebKitApp): Added.
(runSafari): Modified to use webkitdirs::runMacWebKitApp().
(runMiniBrowser): Ditto.
(runWebKitTestRunner): Ditto.
(runTestWebKitAPI): Ditto.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@96448 268f45cc-cd09-0410-ab3c-d52691b4dbfc