1.0.3dev: fixed wrongly `jquery.js` loading on auto-preview when editing ticket comment (refs #10674)

 - Added `$.loadScript` to avoid reloading scripts.
 - Added `$.documentReady` to register `$.ready` listener.
 - If the given script to `$.loadScript` is already loaded, instead call `ready` listeners that are registered using `$.documentReady`.


git-svn-id: http://trac.edgewall.org/intertrac/log:/branches/1.0-stable@13390 af82e41b-90c4-0310-8c96-b1721e28e2e2