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/support/timestamp.h

@@ -0,0 +1,28 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 2015. 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_SUPPORT_TIMESTAMP_H_
+#define WPIUTIL_SUPPORT_TIMESTAMP_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+unsigned long long WPI_Now(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#ifdef __cplusplus
+namespace wpi {
+
+unsigned long long Now();
+
+}  // namespace wpi
+#endif
+
+#endif  // WPIUTIL_SUPPORT_TIMESTAMP_H_