Pull in pthreads library for openbsd (ticket #304)

git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@3158 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishadm/Makefile.am

@@ -12,4 +12,4 @@ varnishadm_SOURCES = \
 varnishadm_LDADD = \
 	$(top_builddir)/lib/libvarnish/libvarnish.la \
 	$(top_builddir)/lib/libvarnishcompat/libvarnishcompat.la \
-	${NET_LIBS}
+	${PTHREAD_LIBS} ${NET_LIBS}