[Ada] Collecting previous instances

[Arnaud Charlet <charlet at adacore dot com>]

When instantiating a nested generic, we must also analyze all previous 
inner instances contained in the encloing instance,  to ensure that the
same set of public symbols is generated under all circumstances. Instantiations
declared within a generic body must be excluded from this.

The following must compile quietly with -O1 or higher optimization levels.

---
with Services;
package P is new Services.Generic_Service_B;
---
package Services is
   generic
   package Generic_Service_A is
      procedure Attach;
   end;

   generic
   package Generic_Service_B is
   end;
end;
---
package body Services is
   generic
   package Service_A_Support is
   end;

   package body Service_A_Support is
      type Wint is record
         Value  : aliased Integer := 0;
      end record;

      type Warray is array (1 .. 1) of Wint;

      type Wrecord is record
         Value : Warray;
      end record;
   end;

   package body Generic_Service_A is
      package Support is new Service_A_Support;
      procedure Attach is begin null; end;
   end;

   generic
   package Service_B_Generic_Support is
      generic
      package Reception_Generic is
         procedure Attach;
      end;
   end;

   package body Service_B_Generic_Support is
      generic
      package Generic_Reception_Generic is
      end;

      package body Generic_Reception_Generic is
         task Sc_Data_Pump is end;
         task body Sc_Data_Pump is begin null; end;
      end;

      package body Reception_Generic is
         package Generic_Reception is new Generic_Reception_Generic;
         procedure Attach is begin null; end Attach;
      end;
   end;

   package Service_B_Support is new Service_B_Generic_Support;

   package body Generic_Service_B is
      package Support is new Service_B_Support.Reception_Generic;
   end;
end;

Tested on x86_64-pc-linux-gnu, committed on trunk

2009-06-22  Ed Schonberg  <schonberg@adacore.com>

	* sem_ch12.adb (Collect_Previous_Instances): Do not collect
	instantiations declared in a previous generic package body.

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