Fix warnings about unused variables in C++ lexer.
Fix warnings about unused variables in C++ lexer.

Change-Id: I8331ff95f5b3c80e15cd71dbce2bb6de17a49c8e
Reviewed-by: Joerg Bornemann <47777b9406dbddd02a3fdca8341789a013805a11@digia.com>

qtproject/qt-labs-qbs,gatzka/qt-labs-qbs,Distrotech/qbs,qtproject/qt-labs-qbs,qt-labs/qbs,gatzka/qt-labs-qbs,qt-labs/qbs,Distrotech/qbs,Distrotech/qbs,qt-labs/qbs,gatzka/qt-labs-qbs,gatzka/qt-labs-qbs,Distrotech/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,villytiger/qbs,qt-labs/qbs,Distrotech/qbs,gatzka/qt-labs-qbs,Distrotech/qbs,gatzka/qt-labs-qbs,villytiger/qbs,qt-labs/qbs,villytiger/qbs,villytiger/qbs,villytiger/qbs,qt-labs/qbs,Distrotech/qbs,qtproject/qt-labs-qbs,villytiger/qbs,gatzka/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs