Problem: C++11 partially supported on gcc 4.8

Solution: Use intrinsic instead of std::is_trivially_copyable for gcc
versions older than 5.

Author: gummif

README.md

@@ -36,7 +36,7 @@ Supported platforms
  - Additional platforms that are known to work:
    - We have no current reports on additional platforms that are known to work yet. Please add your platform here. If CI can be provided for them with a cloud-based CI service working with GitHub, you are invited to add CI, and make it possible to be included in the list above.
  - Additional platforms that probably work:
-   - Any platform supported by libzmq that provides a sufficiently recent gcc (4.8.1 or newer) or clang (3.3 or newer)
+   - Any platform supported by libzmq that provides a sufficiently recent gcc (4.8.1 or newer) or clang (3.4.1 or newer)
    - Visual Studio 2012+ x86/x64
 
 Examples

zmq.hpp

@@ -122,6 +122,14 @@
 #define ZMQ_DELETED_FUNCTION
 #endif
 
+#ifdef ZMQ_CPP11
+#if defined(__GNUC__) && __GNUC__ < 5
+#define ZMQ_IS_TRIVIALLY_COPYABLE(T) __has_trivial_copy(T)
+#else
+#define ZMQ_IS_TRIVIALLY_COPYABLE(T) std::is_trivially_copyable<T>::value
+#endif
+#endif
+
 #if ZMQ_VERSION >= ZMQ_MAKE_VERSION(3, 3, 0)
 #define ZMQ_NEW_MONITOR_EVENT_LAYOUT
 #endif
@@ -331,7 +339,7 @@ class message_t
     template<class Range,
              typename = typename std::enable_if<
                detail::is_range<Range>::value
-               && std::is_trivially_copyable<detail::range_value_t<Range>>::value
+               && ZMQ_IS_TRIVIALLY_COPYABLE(detail::range_value_t<Range>)
                && !std::is_same<Range, message_t>::value>::type>
     explicit message_t(const Range &rng) :
         message_t(detail::ranges::begin(rng), detail::ranges::end(rng))
@@ -948,7 +956,7 @@ template<class T> struct is_pod_like
     // trivially copyable OR standard layout.
     // Here we decide to be conservative and require both.
     static constexpr bool value =
-      std::is_trivially_copyable<T>::value && std::is_standard_layout<T>::value;
+      ZMQ_IS_TRIVIALLY_COPYABLE(T) && std::is_standard_layout<T>::value;
 };
 
 template<class C> constexpr auto seq_size(const C &c) noexcept -> decltype(c.size())