finitel: Use correct GCC builtin

__builtin_isinf_sign doesn't reflect the correct return value for NaN
to emulate finite function.  Use __builtin_isfinite instead whichg is available
since GCC 4.4 just as __builtin_isinf_sign.

	* libm/common/sl_finite.c (finitel): Use __builtin_isfinite.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

newlib/libm/common/sl_finite.c

@@ -19,7 +19,7 @@ finitel (long double x)
      Some architectures for example have an 80-bit long double whereas
      others use 128-bits.  We use macros and comiler builtin functions
      to avoid specific knowledge of the long double format.  */
-  return __builtin_isinf_sign (x) == 0;
+  return __builtin_isfinite (x);
 #endif
 }