Adds JNI call to get CANStatus (#677)

Call already existed in the HAL.

wpilibj/src/test/java/edu/wpi/first/wpilibj/can/CANStatusTest.java

@@ -0,0 +1,19 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2017 FIRST. 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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+package edu.wpi.first.wpilibj.can;
+
+import org.junit.Test;
+
+public class CANStatusTest {
+  @Test
+  public void canStatusGetDoesntThrow() {
+    CANStatus status = new CANStatus();
+    CANJNI.GetCANStatus(status);
+    // Nothing we can assert, so just make sure it didn't throw.
+  }
+}