BUILD/MINOR: haproxy : FreeBSD/cpu affinity needs pthread_np header

for pthread_*_np calls, pthread_np.h is needed under FreeBSD.
diff --git a/src/haproxy.c b/src/haproxy.c
index 891a021..a1fe550 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -55,6 +55,7 @@
 #ifdef __FreeBSD__
 #include <sys/param.h>
 #include <sys/cpuset.h>
+#include <pthread_np.h>
 #endif
 #endif