Remove monotonic_clock replacement macro for gcc-4.6

configure.ac

@@ -170,24 +170,6 @@ AX_CXX_COMPILE_STDCXX_11([noext], [optional])
 
 AC_LANG_PUSH(C++)
 
-# Check that std::chrono::steady_clock is available. In particular,
-# gcc 4.6 does not have one, but has monotonic_clock which is the old
-# name existed in the pre-standard draft. If steady_clock is not
-# available, don't define HAVE_STEADY_CLOCK and replace steady_clock
-# with monotonic_clock.
-AC_MSG_CHECKING([whether std::chrono::steady_clock is available])
-AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
-[[
-#include <chrono>
-]],
-[[
-auto tp = std::chrono::steady_clock::now();
-]])],
-    [AC_DEFINE([HAVE_STEADY_CLOCK], [1],
-               [Define to 1 if you have the `std::chrono::steady_clock`.])
-     AC_MSG_RESULT([yes])],
-    [AC_MSG_RESULT([no])])
-
 # Check that std::future is available.
 AC_MSG_CHECKING([whether std::future is available])
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM(

src/nghttp2_config.h

@@ -29,10 +29,4 @@
 #include <config.h>
 #endif // HAVE_CONFIG_H
 
-// gcc 4.6 has std::chrono::monotonic_clock, which was renamed as
-// std::chrono::steady_clock in C++11 standard.
-#ifndef HAVE_STEADY_CLOCK
-#define steady_clock monotonic_clock
-#endif // !HAVE_STEADY_CLOCK
-
 #endif // NGHTTP2_CONFIG_H