add dma-based edge-counting code

Change-Id: I4414b716357effcfbcabdec2a1a19b57d1f344e6
diff --git a/frc971/wpilib/wpilib_interface.cc b/frc971/wpilib/wpilib_interface.cc
index 42d5882..42f16e8 100644
--- a/frc971/wpilib/wpilib_interface.cc
+++ b/frc971/wpilib/wpilib_interface.cc
@@ -29,6 +29,7 @@
 #include "frc971/wpilib/buffered_solenoid.h"
 #include "frc971/wpilib/buffered_pcm.h"
 #include "frc971/wpilib/gyro_sender.h"
+#include "frc971/wpilib/dma_edge_counting.h"
 #include "frc971/wpilib/interrupt_edge_counting.h"
 
 #include "Encoder.h"