Fix IterativeRobot/TimedRobot RobotInit(). (#633)

In C++, it's not legal to call a virtual function from within a constructor,
so the user override was never called (the base function is always called).

See https://isocpp.org/wiki/faq/strange-inheritance#calling-virtuals-from-ctors

While this is technically allowed in Java, also change Java for consistency.

wpilibj/src/main/java/edu/wpi/first/wpilibj/IterativeRobot.java

@@ -28,7 +28,12 @@ public class IterativeRobot extends IterativeRobotBase {
    * Provide an alternate "main loop" via startCompetition().
    */
   public void startCompetition() {
-    // loop forever, calling the appropriate mode-dependent function
+    robotInit();
+
+    // Tell the DS that the robot is ready to be enabled
+    HAL.observeUserProgramStarting();
+
+    // Loop forever, calling the appropriate mode-dependent function
     while (true) {
       // Wait for new data to arrive
       m_ds.waitForData();

wpilibj/src/main/java/edu/wpi/first/wpilibj/IterativeRobotBase.java

@@ -50,16 +50,6 @@ public abstract class IterativeRobotBase extends RobotBase {
 
   private Mode m_lastMode = Mode.kNone;
 
-  /**
-   * IterativeRobotBase constructor.
-   */
-  public IterativeRobotBase() {
-    robotInit();
-
-    // Tell the DS that the robot is ready to be enabled
-    HAL.observeUserProgramStarting();
-  }
-
   /**
    * Provide an alternate "main loop" via startCompetition().
    */

wpilibj/src/main/java/edu/wpi/first/wpilibj/TimedRobot.java

@@ -39,7 +39,12 @@ public class TimedRobot extends IterativeRobotBase {
    * Provide an alternate "main loop" via startCompetition().
    */
   public void startCompetition() {
-    // loop forever, calling the appropriate mode-dependent function
+    robotInit();
+
+    // Tell the DS that the robot is ready to be enabled
+    HAL.observeUserProgramStarting();
+
+    // Loop forever, calling the appropriate mode-dependent function
     m_startLoop = true;
     m_loop.startPeriodic(m_period);
     while (true) {