Move common utility classes to wpiutil library. (#79)

This is a breaking change to dependencies that use the static ntcore
library.  Unless the wpiutil library is also linked, linker errors will
result.  This does not affect the shared ntcore library.

wpiutil/include/llvm/None.h

@@ -0,0 +1,26 @@
+//===-- None.h - Simple null value for implicit construction ------*- C++ -*-=//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file provides None, an enumerator for use in implicit constructors
+//  of various (usually templated) types to make such construction more
+//  terse.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_NONE_H
+#define LLVM_ADT_NONE_H
+
+namespace llvm {
+/// \brief A simple null object to allow implicit construction of Optional<T>
+/// and similar types without having to spell out the specialization's name.
+enum class NoneType { None };
+const NoneType None = None;
+}
+
+#endif