fix double comparison in histogram test

Summary:
The TestDoubleWidthTooBig test was performing an exact equality check on
two double values. This equality check fails when run on 32-bit
platforms.

Replace the EXPECT_EQ() check with EXPECT_NEAR(), and simply check that
the two values do not differ by more than 1e-14.

Reviewed By: Orvid

Differential Revision: D652767

fbshipit-source-id: 7bf7ed560a4180a2e2d07a6050d1df18e18d1eea

folly/stats/test/HistogramTest.cpp

@@ -200,7 +200,7 @@ TEST(Histogram, TestDoubleWidthTooBig) {
   EXPECT_EQ(1, h.getBucketByIndex(0).count);
   h.addValue(7.5);
   EXPECT_EQ(1, h.getBucketByIndex(2).count);
-  EXPECT_EQ(3.0, h.getPercentileEstimate(0.5));
+  EXPECT_NEAR(3.0, h.getPercentileEstimate(0.5), 1e-14);
 }
 
 // Test that we get counts right