c++17: fix TypeFilter::const_iterator
c++17: fix TypeFilter::const_iterator

MSVC complains about inheriting from std::iterator and suggests
declaring typedefs manually

Change-Id: I19cf1d9efd86fccb53827235d3659ef571d4f8b5
Reviewed-by: Christian Kandeler <3aa99dcdd3f0cac61fb81c2a11771c0cc2497607@qt.io>

qtproject/qt-labs-qbs,qt-labs/qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qt-labs/qbs,qt-labs/qbs,qtproject/qt-labs-qbs