Issue 3118: make test_math pass on Ubuntu/ia64. exp(-745.0) was raising

OverflowError incorrectly on this platform, presumably as a result of
the libm setting errno = ERANGE for this call.

Modules/mathmodule.c

@@ -82,12 +82,17 @@ is_error(double x)
 		 * should return a zero on underflow, and +- HUGE_VAL on
 		 * overflow, so testing the result for zero suffices to
 		 * distinguish the cases).
+		 *
+		 * On some platforms (Ubuntu/ia64) it seems that errno can be
+		 * set to ERANGE for subnormal results that do *not* underflow
+		 * to zero.  So to be safe, we'll ignore ERANGE whenever the
+		 * function result is less than one in absolute value.
 		 */
-		if (x)
+		if (fabs(x) < 1.0)
+			result = 0;
+		else
 			PyErr_SetString(PyExc_OverflowError,
 					"math range error");
-		else
-			result = 0;
 	}
 	else
                 /* Unexpected math error */