Added a README file regarding WinRT support

To note, this file is currently formatted with CRLF line endings, rather than
LF, to allow the file to be viewed with Notepad.

src/libm/s_fabs.c

@@ -0,0 +1,39 @@
+/* @(#)s_fabs.c 5.1 93/09/24 */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+
+#if defined(LIBM_SCCS) && !defined(lint)
+static const char rcsid[] =
+    "$NetBSD: s_fabs.c,v 1.7 1995/05/10 20:47:13 jtc Exp $";
+#endif
+
+/*
+ * fabs(x) returns the absolute value of x.
+ */
+
+#include "math_libm.h"
+#include "math_private.h"
+
+libm_hidden_proto(fabs)
+#ifdef __STDC__
+     double fabs(double x)
+#else
+     double fabs(x)
+     double x;
+#endif
+{
+    u_int32_t high;
+    GET_HIGH_WORD(high, x);
+    SET_HIGH_WORD(x, high & 0x7fffffff);
+    return x;
+}
+
+libm_hidden_def(fabs)