[FIX] autoToc: Couple of fixes for IE8 - header is a property and cannot be set, and String.trim() doesn't seem to exist, so use the jQuery one

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/12.x@47977 b456876b-0849-0410-b77d-98878d47e9d5