libcxx: Rename .hpp files in libcxx/benchmarks to .h

LLVM uses .h as its extension for header files.

Differential Revision: https://reviews.llvm.org/D66509

llvm-svn: 369487
diff --git a/libcxx/benchmarks/deque.bench.cpp b/libcxx/benchmarks/deque.bench.cpp
index 44a492b..0025a33 100644
--- a/libcxx/benchmarks/deque.bench.cpp
+++ b/libcxx/benchmarks/deque.bench.cpp
@@ -11,8 +11,8 @@
 
 #include "benchmark/benchmark.h"
 
-#include "ContainerBenchmarks.hpp"
-#include "GenerateInput.hpp"
+#include "ContainerBenchmarks.h"
+#include "GenerateInput.h"
 
 using namespace ContainerBenchmarks;