PR ada/15803, ada/15805

PR ada/15803, ada/15805

2007-12-19  Ed Schonberg  <schonberg@adacore.com>
	    Gary Dismukes  <dismukes@adacore.com>

	PR ada/15803, ada/15805
	* sem_ch6.adb, sem_ch3.adb (Constrain_Access): In Ada2005, diagnose
	illegal access subtypes when there is a constrained partial view.
	(Check_For_Premature_Usage): New procedure inside
	Access_Subprogram_Declaration for checking that an access-to-subprogram
	type doesn't reference its own name within any formal parameters or
	result type (including within nested anonymous access types).
	(Access_Subprogram_Declaration): Add call to Check_For_Premature_Usage.
	(Sem_Ch3.Analyze_Object_Declaration, Sem_ch6.Process_Formals): if the
	context is an access_to_variable, the expression cannot be an
	access_to_constant.

From-SVN: r131079