add __FreeBSD__ to ifdefs

On FreeBSD the sysmbol __FreeBSD_kernel__ is only defines if a
specific param.h file is included, unlike Debian/kFreeBSD where this
symbol is always defined.  So also compile the FreeBSD specific code
if __FreeBSD__ is defined for FreeBSD 11 & 12 compatibility.
Signed-off-by: Christopher Hall <hsw@ms2.hinet.net>

src/stream_engine.cpp

@@ -149,7 +149,7 @@ zmq::stream_engine_t::~stream_engine_t ()
         wsa_assert (rc != SOCKET_ERROR);
 #else
         int rc = close (s);
-#ifdef __FreeBSD_kernel__
+#if defined(__FreeBSD_kernel__) || defined (__FreeBSD__)
         // FreeBSD may return ECONNRESET on close() under load but this is not
         // an error.
         if (rc == -1 && errno == ECONNRESET)

src/thread.cpp

@@ -152,7 +152,7 @@ void zmq::thread_t::setSchedulingParameters(int priority_, int schedulingPolicy_
 
     rc = pthread_setschedparam(descriptor, policy, &param);
 
-#ifdef __FreeBSD_kernel__
+#if defined(__FreeBSD_kernel__) || defined (__FreeBSD__)
     // If this feature is unavailable at run-time, don't abort.
     if(rc == ENOSYS) return;
 #endif