ada: Make Interrupt and Attach Handlers Obsolescent in VXWorks

ada: Make Interrupt and Attach Handlers Obsolescent in VXWorks

In order to trigger an obsolescent feature warning in
VXWorks if either the pragma or aspect of Interrupt_Handler
or Attach_Handler is used, the spec of the Register_Interrupt_Handler
method needs to be marked as obsolescent in a VXWorks specific
version of the file.

gcc/ada/ChangeLog:

	* libgnarl/s-interr__vxworks.ads (new): A VXWorks specific
	version of the file where Register_Interrupt_Handler is marked
	with the Obsolescent pragma.
	* libgnarl/s-interr__vxworks.adb: Remove pragma Obsoloescent
	that had no effect.
	* Makefile.rtl: Add entries for using the
	libgnarl/s-interr__vxworks.ads file.