perf: use C++ 14 standard

There are a lot of pretty things introduced in 14 standard,
so let's use it.

NO_DOC=<Build change>
NO_TEST=<Build change>
NO_CHANGELOG=<Build change>

perf/CMakeLists.txt

-set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_CXX_STANDARD 14)
 
 find_package(benchmark QUIET)
 if (NOT ${benchmark_FOUND})