Keep the storage.*.* symbols around for vcl4.1

Properly implementing vmod_storage requires the VMOD to
sanction symbols at VCC compile time, and I'd rather not
face that right now.

Fixes #2596

bin/varnishtest/tests/c00078.vtc

@@ -9,7 +9,7 @@ varnish v1 \
     -arg "-ss1=default,1m" \
     -arg "-ss2=default,1m" \
     -arg "-ss0=default,1m" \
-    -syntax 4.0 \
+    -syntax 4.1 \
     -vcl+backend {
 	import vtc;
 	sub vcl_backend_response {

lib/libvcc/vcc_storage.c

@@ -84,7 +84,7 @@ vcc_stevedore(struct vcc *vcc, const char *stv_name)
 
 	CHECK_OBJ_NOTNULL(vcc, VCC_MAGIC);
 	bprintf(buf, "storage.%s", stv_name);
-	sym = VCC_MkSym(vcc, buf, SYM_VAR, VCL_LOW, VCL_40);
+	sym = VCC_MkSym(vcc, buf, SYM_VAR, VCL_LOW, VCL_41);
 	AN(sym);
 	sym->type = STEVEDORE;
 	sym->eval = vcc_Eval_Var;
@@ -94,7 +94,7 @@ vcc_stevedore(struct vcc *vcc, const char *stv_name)
 
 	for (sv = stvars; sv->name != NULL; sv++) {
 		bprintf(buf, "storage.%s.%s", stv_name, sv->name);
-		sym = VCC_MkSym(vcc, buf, SYM_VAR, VCL_LOW, VCL_40);
+		sym = VCC_MkSym(vcc, buf, SYM_VAR, VCL_LOW, VCL_41);
 		AN(sym);
 		sym->type = sv->type;
 		sym->eval = vcc_Eval_Var;