ada: Minor fix in handling of inherited Pre/Post'Class aspect

ada: Minor fix in handling of inherited Pre/Post'Class aspect

Mapping of calls to primitive functions in Pre/Post'Class aspects
inherited by derived types was only testing against controlling formals
of the parent subprogram. This lead to missing some calls, because formals
could be rewritten to that of the derived subprogram before the test
happens.

gcc/ada/ChangeLog:

	* exp_util.adb (Is_Controlling_Formal_Ref): test scope against
	derived subprogram as well.