C++: add test for TranslationUnit::getPosition bug

This test is marked as failing, because the bug is still there. To be
fixed when we re-use the generated token stream of the preprocessor as
input for the parser.

Task-number: QTCREATORBUG-9799
Change-Id: I454a9939aa188a6ff934a11699232f39c828bc7b
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>