make it compile with gcc 7.2

modules/base/src/test_utils/compare_files.cc

modules/config/base.hh

modules/gfx/src/impl/cartoon_renderer.cc

modules/gfx/src/scene.cc

modules/gfx/src/texture.hh

modules/gfx/src/vertex_array.cc

modules/gui/src/data_viewer/data_viewer.hh

modules/gui/src/data_viewer/data_viewer_panel_base.hh

modules/gui/src/data_viewer/drawing_functions.cc

modules/gui/src/data_viewer/fft_panel.hh

modules/gui/src/file_type_dialog.hh

modules/img/alg/src/polar.cc

modules/img/base/src/base.hh

modules/img/base/src/image_handle.cc

modules/img/base/src/image_list.cc

modules/img/base/src/point.hh

modules/img/base/src/raster_image/raster_image.cc

modules/info/src/info_handle.cc

modules/info/src/item_type_cast.hh

modules/io/src/formatted_line.hh