Use C11 *_DECIMAL_DIG macros in libm-test.inc.

Now that we build with -std=gnu11, we can use C11 <float.h> macros
such as FLT_DECIMAL_DIG instead of the GCC predefines such as
__FLT_DECIMAL_DIG__ that are used internally in <float.h>.  This patch
makes libm-test.inc do so.

Tested for x86_64 and x86.

	* math/libm-test.inc (TYPE_DECIMAL_DIG): Use LDBL_DECIMAL_DIG,
	DBL_DECIMAL_DIG and FLT_DECIMAL_DIG instead of __DECIMAL_DIG__,
	__DBL_DECIMAL_DIG__ and __FLT_DECIMAL_DIG__.

ChangeLog

@@ -1,3 +1,9 @@
+2015-10-28  Joseph Myers  <joseph@codesourcery.com>
+
+	* math/libm-test.inc (TYPE_DECIMAL_DIG): Use LDBL_DECIMAL_DIG,
+	DBL_DECIMAL_DIG and FLT_DECIMAL_DIG instead of __DECIMAL_DIG__,
+	__DBL_DECIMAL_DIG__ and __FLT_DECIMAL_DIG__.
+
 2015-10-28  Carlos Eduardo Seo  <cseo@linux.vnet.ibm.com>
 
 	* sysdeps/powerpc/libc-tls.c: New file. Provides __tls_get_addr () in

math/libm-test.inc

@@ -345,12 +345,12 @@ static FLOAT max_valid_error;
    hex digit, in the case of TYPE_HEX_DIG).  When used with printf
    formats where the precision counts only digits after the point, 1
    is subtracted from these values. */
-#define TYPE_DECIMAL_DIG CHOOSE (__DECIMAL_DIG__,	\
-				 __DBL_DECIMAL_DIG__,	\
-				 __FLT_DECIMAL_DIG__,	\
-				 __DECIMAL_DIG__,	\
-				 __DBL_DECIMAL_DIG__,	\
-				 __FLT_DECIMAL_DIG__)
+#define TYPE_DECIMAL_DIG CHOOSE (LDBL_DECIMAL_DIG,	\
+				 DBL_DECIMAL_DIG,	\
+				 FLT_DECIMAL_DIG,	\
+				 LDBL_DECIMAL_DIG,	\
+				 DBL_DECIMAL_DIG,	\
+				 FLT_DECIMAL_DIG)
 #define TYPE_HEX_DIG ((MANT_DIG + 7) / 4)
 
 /* Compare KEY (a string, with the name of a function) with ULP (a