StdLib: Add support for AArch64

- Use some files from ARM version.
- Use NetBSD software floating point library to provide floating point
  operations not handled directly by hardware floating point enabled
  GCC compiler.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Harry Liebel <Harry.Liebel@arm.com>
Reviewed-by: Olivier Martin <Olivier.Martin@arm.com>
Reviewed-by: Daryl McDaniel <edk2-lists@mc2research.org>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18118 6f19259b-4bc3-4df7-8a09-765794883524

StdLib/Include/Aarch64/machine/ieeefp.h

@@ -0,0 +1,45 @@
+/*  $NetBSD: ieeefp.h,v 1.3 2013/04/23 05:42:23 matt Exp $  */
+
+/*
+ * Based on ieeefp.h written by J.T. Conklin, Apr 28, 1995
+ * Public domain.
+ */
+
+#ifndef _AARCH64_IEEEFP_H_
+#define _AARCH64_IEEEFP_H_
+
+#include <LibConfig.h>
+#include <sys/featuretest.h>
+
+#if defined(_NETBSD_SOURCE) || defined(_ISOC99_SOURCE)
+
+#include <machine/fenv.h>
+
+#if !defined(_ISOC99_SOURCE)
+
+/* Exception type (used by fpsetmask() et al.) */
+
+typedef int fp_except;
+
+/* Bit defines for fp_except */
+
+#define FP_X_INV    FE_INVALID      /* invalid operation exception */
+#define FP_X_DZ     FE_DIVBYZERO    /* divide-by-zero exception */
+#define FP_X_OFL    FE_OVERFLOW     /* overflow exception */
+#define FP_X_UFL    FE_UNDERFLOW    /* underflow exception */
+#define FP_X_IMP    FE_INEXACT      /* imprecise (prec. loss; "inexact") */
+
+/* Rounding modes */
+
+typedef enum {
+    FP_RN=FE_TONEAREST,     /* round to nearest representable number */
+    FP_RP=FE_UPWARD,        /* round toward positive infinity */
+    FP_RM=FE_DOWNWARD,      /* round toward negative infinity */
+    FP_RZ=FE_TOWARDZERO     /* round to zero (truncate) */
+} fp_rnd;
+
+#endif /* !_ISOC99_SOURCE */
+
+#endif /* _NETBSD_SOURCE || _ISOC99_SOURCE */
+
+#endif /* _AARCH64_IEEEFP_H_ */