Merge branch 'bug-17816-Build-is-broken-when-using-Qt5'

• bug-17816-Build-is-broken-when-using-Qt5: Move DESIRED_QT_VERSION to the top. Added missing Qxt sources. Fix CMake variable containing target names for modules and test drivers. Fixed VTK Qt5 configuration and enabled Qwt and Qxt Qt5 builds. Use CMAKE_PREFIX_PATH instead of looking for qmake when using Qt5. Updates for constructor changes in Mouse*Event classes Fix missing header Fix broken symbol exports for OpenViewCore and QmlItems modules