Merge branch 'master' into jgrpp

# Conflicts:
#	src/debug.cpp
#	src/lang/russian.txt
#	src/misc_gui.cpp
#	src/os/windows/crashlog_win.cpp
#	src/os/windows/font_win32.cpp
#	src/os/windows/win32.cpp
#	src/rail_cmd.cpp
#	src/window_gui.h

src/widgets/CMakeLists.txt

@@ -46,6 +46,8 @@ add_files(
     screenshot_widget.h
     settings_widget.h
     sign_widget.h
+    slider.cpp
+    slider_func.h
     smallmap_widget.h
     station_widget.h
     statusbar_widget.h