Fix memory leak.

src/parser/grammatical.y

@@ -103,7 +103,7 @@ list:
         ;
 
 pair:
-        IDENTIFIER ASSIGN object        {COUT(DEBUG)<<" IDENTIFIER ASSIGN object\n"; $$=new ObjectPair($1,$3);}
+        IDENTIFIER ASSIGN object        {COUT(DEBUG)<<" IDENTIFIER ASSIGN object\n"; $$=new ObjectPair($1,$3); delete $1;}
         ;
 
 object: