Export "finish" return value to Python

This patch changes the Python "stop" event emission code to also add
the function return value, if it is known.  This happens when the stop
comes from a "finish" command and when the value can be fetched.

The test is in the next patch.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>

gdb/infcmd.c

@@ -1484,23 +1484,6 @@ get_return_value (struct symbol *func_symbol, struct value *function)
   return value;
 }
 
-/* The captured function return value/type and its position in the
-   value history.  */
-
-struct return_value_info
-{
-  /* The captured return value.  May be NULL if we weren't able to
-     retrieve it.  See get_return_value.  */
-  struct value *value;
-
-  /* The return type.  In some cases, we'll not be able extract the
-     return value, but we always know the type.  */
-  struct type *type;
-
-  /* If we captured a value, this is the value history index.  */
-  int value_history_index;
-};
-
 /* Helper for print_return_value.  */
 
 static void