C++14 supports the use of single quotes inserted between integer digits
as a separator. Updates the built-in C++ code model to recognize such
quotes. This fixes highlighting and indentation issues.
Change-Id: Ic35ce93060b96700a11d108dce1f3cf6c4543632
Fixes: QTCREATORBUG-14939
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>