pcbnew: try to compile 'old' DRC alongside the new prototype

pcbnew/class_marker_pcb.h

@@ -33,7 +33,8 @@
 
 #include <class_board_item.h>
 #include <marker_base.h>
-#include <drc/drc_item.h>
+
+class DRC_ITEM;
 
 // Coordinates count for the basic shape marker
 #define MARKER_SHAPE_POINT_COUNT 9

pcbnew/drc/drc_courtyard_tester.cpp

@@ -32,7 +32,7 @@
 #include <widgets/ui_common.h>
 
 #include <memory>
-
+#include <drc/drc_item.h>
 
 DRC_COURTYARD_TESTER::DRC_COURTYARD_TESTER( MARKER_HANDLER aMarkerHandler ) :
         DRC_TEST_PROVIDER( std::move( aMarkerHandler ) )

pcbnew/drc/drc_keepout_tester.cpp

@@ -26,6 +26,7 @@
 
 #include <class_module.h>
 #include <drc/drc.h>
+#include <drc/drc_item.h>
 
 
 DRC_KEEPOUT_TESTER::DRC_KEEPOUT_TESTER( MARKER_HANDLER aMarkerHandler ) :

pcbnew/drc/footprint_tester.cpp

@@ -24,6 +24,7 @@
 #include <fctsys.h>
 #include <netlist_reader/pcb_netlist.h>
 #include <drc/footprint_tester.h>
+#include <drc/drc_item.h>
 
 void TestFootprints( NETLIST& aNetlist, BOARD* aBoard, std::vector<DRC_ITEM*>& aDRCList )
 {