[hal] Implement stub mockdata on RoboRIO (#2575)

This makes it much more user-friendly to use simulation classes without needing
to ifdef for C++ to avoid linker errors or be very careful about construction
to avoid runtime errors in Java.

hal/src/main/native/athena/mockdata/SimDeviceData.cpp

@@ -0,0 +1,78 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019-2020 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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "hal/simulation/SimDeviceData.h"
+
+#include "hal/simulation/SimDataValue.h"
+
+extern "C" {
+
+void HALSIM_SetSimDeviceEnabled(const char* prefix, HAL_Bool enabled) {}
+
+HAL_Bool HALSIM_IsSimDeviceEnabled(const char* name) { return false; }
+
+int32_t HALSIM_RegisterSimDeviceCreatedCallback(
+    const char* prefix, void* param, HALSIM_SimDeviceCallback callback,
+    HAL_Bool initialNotify) {
+  return 0;
+}
+
+void HALSIM_CancelSimDeviceCreatedCallback(int32_t uid) {}
+
+int32_t HALSIM_RegisterSimDeviceFreedCallback(
+    const char* prefix, void* param, HALSIM_SimDeviceCallback callback) {
+  return 0;
+}
+
+void HALSIM_CancelSimDeviceFreedCallback(int32_t uid) {}
+
+HAL_SimDeviceHandle HALSIM_GetSimDeviceHandle(const char* name) { return 0; }
+
+const char* HALSIM_GetSimDeviceName(HAL_SimDeviceHandle handle) { return ""; }
+
+HAL_SimDeviceHandle HALSIM_GetSimValueDeviceHandle(HAL_SimValueHandle handle) {
+  return 0;
+}
+
+void HALSIM_EnumerateSimDevices(const char* prefix, void* param,
+                                HALSIM_SimDeviceCallback callback) {}
+
+int32_t HALSIM_RegisterSimValueCreatedCallback(HAL_SimDeviceHandle device,
+                                               void* param,
+                                               HALSIM_SimValueCallback callback,
+                                               HAL_Bool initialNotify) {
+  return 0;
+}
+
+void HALSIM_CancelSimValueCreatedCallback(int32_t uid) {}
+
+int32_t HALSIM_RegisterSimValueChangedCallback(HAL_SimValueHandle handle,
+                                               void* param,
+                                               HALSIM_SimValueCallback callback,
+                                               HAL_Bool initialNotify) {
+  return 0;
+}
+
+void HALSIM_CancelSimValueChangedCallback(int32_t uid) {}
+
+HAL_SimValueHandle HALSIM_GetSimValueHandle(HAL_SimDeviceHandle device,
+                                            const char* name) {
+  return 0;
+}
+
+void HALSIM_EnumerateSimValues(HAL_SimDeviceHandle device, void* param,
+                               HALSIM_SimValueCallback callback) {}
+
+const char** HALSIM_GetSimValueEnumOptions(HAL_SimValueHandle handle,
+                                           int32_t* numOptions) {
+  *numOptions = 0;
+  return nullptr;
+}
+
+void HALSIM_ResetSimDeviceData(void) {}
+
+}  // extern "C"