Make vrt.h standalone again, and add test to ensure it stays that way.

Fixes #2250

include/Makefile.am

@@ -124,13 +124,21 @@ CLEANFILES = \
 	tbl/vrt_stv_var.h \
 	vcl.h \
 	vrt_obj.h \
-	vmod_abi.h
+	vmod_abi.h \
+	vrt_test \
+	_vrt_test
 
-TESTS = vbm_test
+TESTS = vbm_test vrt_test
 
 noinst_PROGRAMS = ${TESTS}
 
 vbm_test_SOURCES = vbm_test.c vbm.h
 
+vrt_test_SOURCES =
+
+vrt_test:
+	echo "exec ${CC} -c -o _vrt_test $(top_srcdir)/include/vrt.h" > vrt_test
+	chmod +x vrt_test
+
 test: ${TESTS}
 	@for test in ${TESTS} ; do ./$${test} ; done

include/vrt.h

@@ -65,6 +65,10 @@
 
 /***********************************************************************/
 
+#ifndef __v_printflike
+#  define __v_printflike(a,b)
+#endif
+
 struct VCL_conf;
 struct vrt_acl;
 struct busyobj;