PR ada/23646

	* s-mastop-tru64.adb, s-mastop-irix.adb, s-mastop-vms.adb
	(Enter_Handler, Set_Signal_Machine_State): Removed, no longer used.
	Remove reference to System.Exceptions.

	* s-mastop-x86.adb: Removed, no longer used.

	* s-traceb-mastop.adb: Adjust calls to Pop_Frame.

	* a-excach.adb: Minor reformatting.

	* a-except.ads, a-except.adb: Remove global Warnings (Off) pragma, and
	instead fix new warnings that were hidden by this change.
	(AAA, ZZZ): Removed, replaced by...
	(Code_Address_For_AAA, Code_Address_For_ZZZ): ... these functions, who
	are used instead of constants, to help make Ada.Exception truly
	preelaborate.
	(Rcheck_*, Raise_Constraint_Error, Raise_Program_Error,
	Raise_Storage_Error): File is now a System.Address, to simplify code.
	(Elab code): Removed, no longer used.
	(Null_Occurrence): Remove Warnings Off and make this construct
	preelaborate.
	Remove code related to front-end zero cost exception handling, since
	it is no longer used.
	Remove -gnatL/-gnatZ switches.

	* a-exexda.adb (Append_Info_Exception_Name, Set_Exception_C_Msg):
	Update use of Except.Msg.

	* gnat1drv.adb, inline.adb, bindgen.adb, debug.adb, exp_ch11.ads,
	freeze.adb, frontend.adb, lib.adb, exp_ch11.adb: Remove code related
	to front-end zero cost exception handling, since it is no longer used.
	Remove -gnatL/-gnatZ switches.

	* lib-writ.ads: Minor reformatting
	Remove doc of UX

	* Makefile.rtl: Remove references to s-except*, s-mastop-x86*

	* Make-lang.in: Remove references to s-except.ads

	* s-except.ads: Removed, no longer used.

	* s-mastop.ads, s-mastop.adb:
	(Enter_Handler, Set_Signal_Machine_State): Removed, no longer used.
	Remove reference to System.Exceptions.

	* raise.h, usage.adb, targparm.adb, targparm.ads, switch-m.adb,
	switch-b.adb: Remove code related to front-end zero cost exception
	handling, since it is no longer used.
	Remove -gnatL/-gnatZ switches.

From-SVN: r103848