Add missing <iterator> include in stlutils.h
Add missing <iterator> include in stlutils.h

We're using std::begin() and std::end() here.
The default implementations are provided by
the <iterator> header.

Change-Id: I0acf850f5392fa9e1016aa1c87691d674273df80
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,qt-labs/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs