PR libstdc++/80506 fix constant used in condition

	PR libstdc++/80506
	* include/bits/random.tcc (gamma_distribution::operator()): Fix magic
	number used in loop condition.

From-SVN: r247099

libstdc++-v3/ChangeLog

 2017-04-24  Jonathan Wakely  <jwakely@redhat.com>
 
+	PR libstdc++/80506
+	* include/bits/random.tcc (gamma_distribution::operator()): Fix magic
+	number used in loop condition.
+
 	PR libstdc++/80504
 	* include/bits/refwrap.h (ref, cref): Qualify calls.
 	* testsuite/20_util/reference_wrapper/80504.cc: New test.

libstdc++-v3/include/bits/random.tcc

@@ -2356,7 +2356,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	    __v = __v * __v * __v;
 	    __u = __aurng();
 	  }
-	while (__u > result_type(1.0) - 0.331 * __n * __n * __n * __n
+	while (__u > result_type(1.0) - 0.0331 * __n * __n * __n * __n
 	       && (std::log(__u) > (0.5 * __n * __n + __a1
 				    * (1.0 - __v + std::log(__v)))));