exp_ch2.adb: Remove "with" and "use" clauses for Namet and Snames.

exp_ch2.adb: Remove "with" and "use" clauses for Namet and Snames.

2007-04-20  Hristian Kirtchev  <kirtchev@adacore.com>
	    Robert Dewar  <dewar@adacore.com>
	    Ed Schonberg  <schonberg@adacore.com>
	    Gary Dismukes  <dismukes@adacore.com>

	* exp_ch2.adb: Remove "with" and "use" clauses for Namet and Snames.
	Add "with" and "use" clauses for Sem_Attr.
	(Expand_Current_Value): Do not replace occurences of attribute
	references where the prefix must be a simple name.

	* sem_attr.ads, sem_attr.adb: Remove "with" and "use" clauses for
	Namet. Add new arrays Attribute_Name_Modifies_Prefix and
	Attribute_Requires_Simple_Name_Prefix.
	(Name_Modifies_Prefix): Body of new function.
	(Requires_Simple_Name_Prefix): Body of new function.
	(Resolve_Attribute, case Access): Improve error message for case of
	mismatched conventions.
	(Analyze_Attribute, case 'Tag): The prefix the attribute cannot be of an
	incomplete type.
	(Analyze_Attribute, case 'Access): If the type of the prefix is a
	constrained subtype for a nominal unconstrained type, use its base type
	to check for conformance with the context.
	(Resolve_Attribute): Remove test of the access type being associated
	with a return statement from condition for performing accessibility
	checks on access attributes, since this case is now captured by
	Is_Local_Anonymous_Access.
	(Analyze_Access_Attribute): Set Address_Taken on entity
	(Analyze_Attribute, case Address): Set Address_Taken on entity
	(OK_Self_Reference): Traverse tree to locate enclosing aggregate when
	validating an access attribute whose prefix is a current instance.
	(Resolve_Attribute): In case of attributes 'Code_Address and 'Address
	applied to dispatching operations, if freezing is required then we set
	the attribute Has_Delayed_Freeze in the prefix's entity.
	(Check_Local_Access): Set flag Suppress_Value_Tracking_On_Call in
	current scope if access of local subprogram taken
	(Analyze_Access_Attribute): Check legality of self-reference even if the
	expression comes from source, as when a single component association in
	an aggregate has a box association.
	(Resolve_Attribute, case 'Access): Do not apply accessibility checks to
	the prefix if it is a protected operation and the attribute is
	Unrestricted_Access.
	(Resolve_Attribute, case 'Access): Set the Etype of the attribute
	reference to the base type of the context, to force a constraint check
	when the context is an access subtype with an explicit constraint.
	(Analyze_Attribute, case 'Class): If the prefix is an interface and the
	node is rewritten as an interface conversion. leave unanalyzed after
	resolution, to ensure that type checking against the context will take
	place.

From-SVN: r125395