Make sure vmod.h is distributed as well

git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@5020 d4fa192b-c00b-0410-8231-f00ffab90ce4

include/Makefile.am

@@ -45,6 +45,7 @@ nobase_noinst_HEADERS = \
 	vlu.h \
 	vbm.h \
 	vmb.h \
+	vmod.h \
 	vre.h \
 	vrt.h \
 	vrt_obj.h \