Added ahal

This is a formatted copy of WPILib's default user-visible C++ API, with
a bit of completely unnecessary functionality stripped out. Most of the
stripping so far is only related to weird threading decisions.

Change-Id: Icbfd949b48cd115561862cb909bcc572aba0e753
diff --git a/frc971/wpilib/ahal/SPI.h b/frc971/wpilib/ahal/SPI.h
new file mode 100644
index 0000000..c1172ce
--- /dev/null
+++ b/frc971/wpilib/ahal/SPI.h
@@ -0,0 +1,71 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 2008-2017. All Rights Reserved.                        */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include "HAL/SPI.h"
+
+namespace frc {
+
+class DigitalOutput;
+class DigitalInput;
+
+/**
+ * SPI bus interface class.
+ *
+ * This class is intended to be used by sensor (and other SPI device) drivers.
+ * It probably should not be used directly.
+ *
+ */
+class SPI {
+ public:
+  enum Port : int32_t {
+    kOnboardCS0 = 0,
+    kOnboardCS1,
+    kOnboardCS2,
+    kOnboardCS3,
+    kMXP
+  };
+  explicit SPI(Port SPIport);
+  virtual ~SPI();
+
+  SPI(const SPI &) = delete;
+  SPI &operator=(const SPI &) = delete;
+
+  void SetClockRate(double hz);
+
+  void SetMSBFirst();
+  void SetLSBFirst();
+
+  void SetSampleDataOnFalling();
+  void SetSampleDataOnRising();
+
+  void SetClockActiveLow();
+  void SetClockActiveHigh();
+
+  void SetChipSelectActiveHigh();
+  void SetChipSelectActiveLow();
+
+  virtual int Write(uint8_t *data, int size);
+  virtual int Read(bool initiate, uint8_t *dataReceived, int size);
+  virtual int Transaction(uint8_t *dataToSend, uint8_t *dataReceived, int size);
+
+ protected:
+#ifdef WPILIB2017
+  int m_port;
+#else
+  HAL_SPIPort m_port;
+#endif
+  bool m_msbFirst = false;          // default little-endian
+  bool m_sampleOnTrailing = false;  // default data updated on falling edge
+  bool m_clk_idle_high = false;     // default clock active high
+
+ private:
+  void Init();
+};
+
+}  // namespace frc