artf4127: Implemented velocity PID controller

Change-Id: I8c0f84422f7ca0ac5c50fddb282fb3452ee1d491

wpilibc/wpilibC++/src/PIDSource.cpp

@@ -0,0 +1,21 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 2008. 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 $(WIND_BASE)/WPILib.  */
+/*----------------------------------------------------------------------------*/
+
+#include "PIDSource.h"
+
+/**
+ * Set which parameter you are using as a process control variable.
+ *
+ * @param pidSource An enum to select the parameter.
+ */
+void PIDSource::SetPIDSourceType(PIDSourceType pidSource) {
+  m_pidSource = pidSource;
+}
+
+PIDSourceType PIDSource::GetPIDSourceType() const {
+  return m_pidSource;
+}