[committed] libstdc++: Use 2 * epsilon step for piecewise_constant_distribution tests.

[Tomasz Kamiński]

This is required to pass test on powerpc64le-unknown-linux-gnu, and
was already the case for piecewise_linear_distribution.

libstdc++-v3/ChangeLog:

        * 
testsuite/26_numerics/random/piecewise_constant_distribution/operators/accessors.cc
        (test_precision_depended): Define step as 2 * epsilon().
---
epsilon() is the value "that can be added to one", we are also 
substracting it. 

Pushed to trunk. Modified test passed both on powerpc and x86_64-linux.

 .../piecewise_constant_distribution/operators/accessors.cc      | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git 
a/libstdc++-v3/testsuite/26_numerics/random/piecewise_constant_distribution/operators/accessors.cc
 
b/libstdc++-v3/testsuite/26_numerics/random/piecewise_constant_distribution/operators/accessors.cc
index 15fb6821749..b31b028dc27 100644
--- 
a/libstdc++-v3/testsuite/26_numerics/random/piecewise_constant_distribution/operators/accessors.cc
+++ 
b/libstdc++-v3/testsuite/26_numerics/random/piecewise_constant_distribution/operators/accessors.cc
@@ -50,7 +50,7 @@ test_precision_depended()
 
   std::initializer_list<DistType> x{0.0, 0.5, 1.0};
   constexpr InputType step
-    = std::numeric_limits<InputType>::epsilon();
+    = std::numeric_limits<InputType>::epsilon() * 2;
   InputType wt[2]{InputType(1) - step, InputType(1) + step};
 
   using Distribution = std::piecewise_constant_distribution<DistType>;
-- 
2.55.0