This will eventually fix a few leaks we introduced in the semantic highlighter.

Main reason is that find-usages and refactoring broke completely.
Second reason is that concurrent modification was done on the
children-list while deleting/destructing.

This reverts commit b0b95f88.

Patch by: Bill King

Task-number: QTCREATORBUG-384
Reviewed-by: Thorbjørn Lindeijer <thorbjorn.lindeijer@nokia.com>

Now, the ASTVisitor constructor takes a valid reference to a TranslationUnit.

Done with Erik Verbruggen

Done with Erik Verbruggen

Done with Erik Verbruggen