patch 8.1.0477: tiny build fails

Problem:    Tiny build fails.
Solution:   Add a dummy declaration for funccal_entry_T.
diff --git a/src/structs.h b/src/structs.h
index ebd94c3..560ce42 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1445,6 +1445,10 @@
 {
     int	    dummy;
 } funcdict_T;
+typedef struct
+{
+    int	    dummy;
+} funccal_entry_T;
 #endif
 
 struct partial_S