[Ada] Handling of fully private protected operations

[Arnaud Charlet <charlet at adacore dot com>]

An operation declared in a protected body is not directly accessible to a
user of the protected object, and it would appear that there is no need to
provide a locking version of the operation. However, it is possible to
use 'Access from within the protected body to pass a pointer to the internal
operation outside of the object, in order to provide a callback facility.
This idiom is used with Ada2005 Timing_Events for example. This patch ensures
that a locking version of such a private operation is always provided, so that
it is available to analyze an 'Access attribute within the same protectedy body.

The following must compile quietly:
---
with Ada.Real_Time.Timing_Events;
package Alarm_Clock is
   protected type Alarm_Type is
      procedure Set;
      entry Wait;
   end Alarm_Type;
end Alarm_Clock;
---
package body Alarm_Clock is 
   use Ada.Real_Time;
   Timer: Timing_Events.Timing_Event;
   Fired: Boolean := False;
  
   protected body Alarm_Type is

      procedure Wakeup (Event: in out Timing_Events.Timing_Event) is
      begin
         Fired := True;
      end Wakeup;

      procedure Set is
      begin
         Timer.Set_Handler (In_Time => Seconds (2),
                             Handler => Wakeup'Access);
      end;

      entry Wait when Fired is
      begin
         null;
      end Wait;
   end Alarm_Type;
end Alarm_Clock;

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

2009-11-30  Ed Schonberg  <schonberg@adacore.com>

	* exp_ch9.ads (Build_Private_Protected_Declaration): For a protected
	operation that is only declared in a protected body, create a
	corresponding subprogram declaration.
	* exp_ch9.adb (Expand_N_Protected_Body): Create protected body of
	operation in all cases, including for an operation that is only
	declared in the body.
	* sem_ch6.adb: Call Build_Private_Protected_Declaration
	* exp_ch6.adb (Expand_N_Subprogram_Declaration): For an operation
	declared in a protected body, create the declaration for the
	corresponding protected version of the operation.

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