Refactor bug-strtod.c to better test new types.

This introduces tst-strtod.h to contain some macros
to assist with updating strto{f,d,ld} test code to
support additional variants of this function.

stdlib/tst-strtod.h

@@ -0,0 +1,50 @@
+/* Common utilities for testing strtod and its derivatives.
+   This file is part of the GNU C Library.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _TST_STRTOD_H
+#define _TST_STRTOD_H
+
+#define FSTRLENMAX 128
+
+/* Splat n variants of the same test for the various strtod functions.  */
+#define GEN_TEST_STRTOD_FOREACH(mfunc)		  \
+    mfunc (  f,       float, snprintf,  "", f, f) \
+    mfunc (  d,      double, snprintf,  "",  ,  ) \
+    mfunc ( ld, long double, snprintf, "L", L, l)
+/* The arguments to the generated macros are:
+   FSUF - Function suffix
+   FTYPE - float type
+   FTOSTR - float to string func
+   FTOSTRM - Optional modifier for FTOSTR format
+   LSUF - Literal suffix
+   CSUF - C standardish suffix for many of the math functions
+*/
+
+
+
+#define STRTOD_TEST_FOREACH(mfunc, ...)	  \
+({					  \
+   int result = 0;			  \
+   result |= mfunc ## f  (__VA_ARGS__);   \
+   result |= mfunc ## d  (__VA_ARGS__);   \
+   result |= mfunc ## ld (__VA_ARGS__);   \
+   result;				  \
+})
+
+
+#endif