[Ada] Fix problems with deferred constants and address clauses

[Eric Botcazou]

The Ada compiler accepts address clauses on deferred constants, e.g.

package P is

  C : constant Natural := 1;

  C2 : constant Natural;
  for C2'Address use C'Address;

private
  C2 : constant Natural := 1;

end P;

but it was not honoring them in all cases and was even ICEing on some 
particular form.  The attached patch should fix that by specializing
their handling in Gigi.

Tested on i586-suse-linux, applied on the mainline.


2008-08-01  Eric Botcazou  <ebotcazou@adacore.com>

	* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Constant>: Remove dead
	code.  Do not get full definition of deferred constants with address
	clause for a use.  Do not ignore deferred constant definitions with
	address clause.  Ignore constant definitions already marked with the
	error node.
	<object>: Remove obsolete comment.  For a deferred constant with
	address clause, get the initializer from the full view.
	* gcc-interface/trans.c (gnat_to_gnu) <N_Attribute_Definition_Clause>:
	Rework and remove obsolete comment.
	<N_Object_Declaration>: For a deferred constant with address clause,
	mark the full view with the error node.
	* gcc-interface/utils.c (convert_to_fat_pointer): Rework and fix
	formatting nits.


2008-08-01  Eric Botcazou  <ebotcazou@adacore.com>

	* gnat.dg/deferred_const1.adb: New test.
	* gnat.dg/deferred_const2.adb: Likewise.
	* gnat.dg/deferred_const2_pkg.ad[sb]: New helper.
	* gnat.dg/deferred_const3.adb: New test.
	* gnat.dg/deferred_const3_pkg.ad[sb]: New helper.


-- 
Eric Botcazou
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