Move GetStackTrace and Demangle to wpiutil, add Windows support (#1819)

For Windows, import the StackWalker source (https://github.com/JochenKalmbach/StackWalker)
plus PR 35 in that repo, with a few simplifications to StackWalker.h.

wpiutil/src/main/native/include/wpi/Demangle.h

@@ -0,0 +1,25 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2008-2019 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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#ifndef WPIUTIL_WPI_DEMANGLE_H_
+#define WPIUTIL_WPI_DEMANGLE_H_
+
+#include <string>
+
+namespace wpi {
+
+/**
+ * Demangle a C++ symbol.
+ *
+ * @param mangledSymbol the mangled symbol.
+ * @return The demangled symbol, or mangledSymbol if demangling fails.
+ */
+std::string Demangle(char const* mangledSymbol);
+
+}  // namespace wpi
+
+#endif  // WPIUTIL_WPI_DEMANGLE_H_

wpiutil/src/main/native/include/wpi/StackTrace.h

@@ -0,0 +1,24 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2008-2019 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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#ifndef WPIUTIL_WPI_STACKTRACE_H_
+#define WPIUTIL_WPI_STACKTRACE_H_
+
+#include <string>
+
+namespace wpi {
+
+/**
+ * Get a stack trace, ignoring the first "offset" symbols.
+ *
+ * @param offset The number of symbols at the top of the stack to ignore
+ */
+std::string GetStackTrace(int offset);
+
+}  // namespace wpi
+
+#endif  // WPIUTIL_WPI_STACKTRACE_H_