sem_ch7.adb (Check_Anonymous_Access_Types): Fix error for null body

2007-04-20  Robert Dewar  <dewar@adacore.com>
	    Javier Miranda  <miranda@adacore.com>

	* sem_ch7.adb (Check_Anonymous_Access_Types): Fix error for null body
	(Derive_Inherited_Private_Subprogram): Code cleanup. In case of explicit
	overriding of an inherited private subprogram now there is no need to
	inherit its dispatching slot and reduce the size of the dispatch table.
	Set_All_DT_Position now ensures that the same slot is now assigned to
	both entities. This is required to statically build the dispatch table.
	(Declare_Inherited_Private_Subprograms): Rewriten to avoid the need
	of calling Set_All_DT_Position to re-evaluate the position of the
	entries in the dispatch table. Such reevaluation is not desired if
	the tagged type is already frozen.

From-SVN: r125452