Use NO_VXID instead of literal 0 VXID

See varnish-cache 7f28888779fd14f99eb34e50f6fb07ea6bbff999

src/vmod_re.c

@@ -59,6 +59,11 @@ typedef struct ov_s {
 	int			ovector[MAX_OV];
 } ov_t;
 
+// varnish-cache pre 7f28888779fd14f99eb34e50f6fb07ea6bbff999
+#ifndef NO_VXID
+#define NO_VXID (0U)
+#endif
+
 static void
 errmsg(VRT_CTX, const char *fmt, ...)
 {
@@ -69,7 +74,7 @@ errmsg(VRT_CTX, const char *fmt, ...)
 	if (ctx->vsl)
 		VSLbv(ctx->vsl, SLT_VCL_Error, fmt, args);
 	else
-		VSLv(SLT_VCL_Error, 0, fmt, args);
+		VSLv(SLT_VCL_Error, NO_VXID, fmt, args);
 	va_end(args);
 }