Started work on splitting out .cpp files from header files

include/internal/catch_errno_guard.cpp

@@ -0,0 +1,15 @@
+/*
+ *  Created by Martin on 06/03/2017.
+ *
+ *  Distributed under the Boost Software License, Version 1.0. (See accompanying
+ *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+ */
+
+#include "catch_errno_guard.h"
+
+#include <cerrno>
+
+namespace Catch {
+        ErrnoGuard::ErrnoGuard():m_oldErrno(errno){}
+        ErrnoGuard::~ErrnoGuard() { errno = m_oldErrno; }
+}