ada: Make Interrupt_State not require Ada.Interrupts

This makes it so using the Interrupt_State configuration pragma does not
add an implicit dependency to Ada.Interrupts. The rationale is given in
a comment.

gcc/ada/ChangeLog:

	* libgnarl/s-inttyp.ads: New file.
	* libgnarl/a-interr.ads (Interrupt_ID): Derive from
	Preelab_Interrupt_ID.
	* libgnarl/s-interr.ads (Interrupt_ID): Derive from
	Preelab_Interrupt_ID.
	(Ada_Interrupt_ID): Remove.
	* libgnarl/s-interr__vxworks.ads (Ada_Interrupt_ID): Remove.
	* xsintnam.sed: New file.
	* Makefile.rtl: Register new runtime files.
	* libgnarl/a-interr.adb: Adjust with clauses.
	* rtsfind.ads (RE_Interrupt_Names, RE_Preelab_Interrupt_ID): New
	variants.
	* sem_prag.adb: Use entities from new preelaborate packages.
	* gcc-interface/Makefile.in: Generate System.Interrupt_Names.