ada: Missing support for 'Old with overloaded function

ada: Missing support for 'Old with overloaded function

The compiler reports an error when the prefix of 'Old is
a call to an overloaded function that has no parameters.

gcc/ada/

	* sem_attr.adb (Analyze_Attribute): Enhance support for
	using 'Old with a prefix that references an overloaded
	function that has no parameters; add missing support
	for the use of 'Old within qualified expressions.

	* sem_util.ads (Preanalyze_And_Resolve_Without_Errors):
	New subprogram.

	* sem_util.adb (Preanalyze_And_Resolve_Without_Errors):
	New subprogram.