* ali.adb: Type reference does not reset current file.

	* ali.adb: Recognize and scan renaming reference

	* ali.ads: Add spec for storing renaming references.

	* lib-xref.ads: Add documentation for handling of renaming references

	* lib-xref.adb: Implement output of renaming reference.

	* checks.adb:
	(Determine_Range): Document local variables
	(Determine_Range): Make sure Hbound is initialized. It looks as though
	 there could be a real problem here with an uninitialized reference
	 to Hbound, but no actual example of failure has been found.

	* g-socket.ads:
	Fix comment of Shutdown_Socket and Close_Socket. These functions
	should not fail silently because if they are called twice, this
	probably means that there is a race condition in the user program.
	Anyway, this behaviour is consistent with the rest of this unit.
	When an error occurs, an exception is raised with the error message
	as exception message.

From-SVN: r48125