* exp_dist.adb (Build_RPC_Receiver_Body): New subprogram. This
	procedures factors the common processing for building an RPC receiver
	for an RCI package or an RACW type.
	Stylistic cleanup: change '/= Empty' to 'Present ()'; move body of
	Build_Remote_Subprogram_Proxy_Type into proper alphabetical order.
	(Get_PCS_Name): New subprogram. Returns the name of the PCS currently
	in use.
	(Specific_Add_RACW_Features): New subprogram. PCS-specific part of
	Add_RACW_Features.
	(Specific_Add_RAST_Features): New subprogram. PCS-specific part of
	Add_RAST_Features.
	(Assign_Subprogram_Identifier): New subprogram. Provision for assigning
	distribution subprogram identifiers that are either subprogram numbers
	or strings.
	(Get_Subprogram_Ids): New subprogram. Retrieve both the numeric and
	string distribution identifiers assigned to a given subprogram.
	(Get_Subprogram_Id): Reimplement in terms of Get_Subprogram_Ids.
	(Add_RAS_Dereference_TSS): Add comments.
	(Build_General_Calling_Stubs): Note that the RACW_Type formal parameter
	is not referenced yet because it will be used by the PolyORB DSA
	implementation.
	(Insert_Partition_Check): Remove fossile code.
	(First_RCI_Subprogram_Id): Document this constant.
	(Add_RAS_Access_TSS): Correct the setting of the Etype of the
	RAS_Access TSS.
	(Get_Pkg_Name_String): Remove subprogram. Usage occurrences are
	replaced with calls to Get_Library_Unit_Name_String. Previously there
	were several instances of the same code in different locations in the
	compiler; this checkin completes the replacement of all of these
	instances with calls to a common subprogram.
	Minor reformatting.

	* sem_dist.adb: Remove comment noting that RPC receiver generation
	should be disabled for RACWs that implement RASs.
	(Process_Partition_Id): Use new subprogram Get_Library_Unit_Name_String.

	* sem_util.ads, sem_util.adb (Has_Stream): New function
	(Get_Library_Unit_Name_String): New subprogram to retrieve the fully
	qualified name of a library unit into the name buffer.
	(Note_Possible_Modification): Generate a reference only
	if the context comes from source.

	* snames.ads (PCS_Names): New subtype corresponding to names of
	supported implementations of the Partition Communication Subsystem
	(PCS) (i.e. the runtime library support modules for the distributed
	systems annex).

From-SVN: r90903