patch 8.2.3991: Vim9: error when extending dict<any>

Problem:    Vim9: error when extending dict<any> with another type that it was
            initialized with.
Solution:   Also set the type for dict<any> if the initializer has a more
            specific type. (closes #9461)
diff --git a/src/vim9.h b/src/vim9.h
index d2c23be..2ae3f42 100644
--- a/src/vim9.h
+++ b/src/vim9.h
@@ -725,3 +725,7 @@
 				    // lhs_name is not NULL
 };
 
+// flags for typval2type()
+#define TVTT_DO_MEMBER	    1
+#define TVTT_MORE_SPECIFIC  2	// get most specific type for member
+