Merge branch 'progsig-sx' into jgrpp

Conflicts:
	src/command.cpp
	src/command_type.h
	src/lang/english.txt
	src/rail_cmd.cpp
	src/rail_gui.cpp
	src/saveload/extended_ver_sl.cpp
	src/saveload/extended_ver_sl.h
	src/saveload/saveload.cpp
	src/widgets/rail_widget.h
	src/window_type.h

src/saveload/extended_ver_sl.h

@@ -22,6 +22,7 @@
 enum SlXvFeatureIndex {
 	XSLFI_NULL                          = 0,      ///< Unused value, to indicate that no extended feature test is in use
 	XSLFI_TRACE_RESTRICT,                         ///< Trace restrict
+	XSLFI_PROG_SIGS,                              ///< programmable signals patch
 
 	XSLFI_SIZE,                                   ///< Total count of features, including null feature
 };