Problem: including recent "zmq_utils.h" crashes gcc -pedantic jobs

Problem: Recent deprecation of the "zmq_utils.h" header file caused pedantic compilations (including czmq) to fail because non-portable #warning is used.
Solution: Limit the deprecation warnings to compilers known or assumed to support the "#pragma message" (GCC, MSVC, CLANG) and wrap with GCC directives to not treat these warnings as errors on paranoid builds.

include/zmq_utils.h

@@ -28,9 +28,21 @@
 */
 
 /*  This file is deprecated, and all its functionality provided by zmq.h     */
+/*  Note that -Wpedantic compilation requires GCC to avoid using its custom
+    extensions such as #warning, hence the trick below. Also, pragmas for
+    warnings or other messages are not standard, not portable, and not all
+    compilers even have an equivalent concept.
+    So in the worst case, this include file is treated as silently empty. */
 
-#ifndef _MSC_VER
-#warning(zmq_utils.h is deprecated.All its functionality is provided by zmq.h.)
-#else
+#if defined(__clang__) || defined(__GNUC__) || defined(__GNUG__) || defined(_MSC_VER)
+#if defined(__GNUC__) || defined(__GNUG__)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic warning "-Wcpp"
+#pragma GCC diagnostic ignored "-Werror"
+#pragma GCC diagnostic ignored "-Wall"
+#endif
 #pragma message("Warning: zmq_utils.h is deprecated. All its functionality is provided by zmq.h.")
+#if defined(__GNUC__) || defined(__GNUG__)
+#pragma GCC diagnostic pop
+#endif
 #endif