qlogging: Fix build on FreeBSD after 63cd16d.

pthread_getthreadid_np(3) is defined in pthread_np.h, not pthread.h.
Additionally, it was added during the FreeBSD 9 time frame, so add a
version check to use it only when we know it is present.

Change-Id: I4d716d9bfb189d10128b6d458a47045e130b51e8
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

src/corelib/global/qlogging.cpp

@@ -103,8 +103,8 @@ static int qt_gettid()
     pthread_threadid_np(NULL, &tid);
     return tid;
 }
-#elif defined(Q_OS_FREEBSD_KERNEL)
-#  include <pthread.h>
+#elif defined(Q_OS_FREEBSD_KERNEL) && defined(__FreeBSD_version) && __FreeBSD_version >= 900031
+#  include <pthread_np.h>
 static int qt_gettid()
 {
     return pthread_getthreadid_np();