2007-12-06  Eric Botcazou  <ebotcazou@adacore.com>
	    Bob Duff  <duff@adacore.com>
	    Tristan Gingold  <gingold@adacore.com>

	* system-linux-ia64.ads, system-freebsd-x86.ads, system-lynxos-ppc.ads, 
	system-lynxos-x86.ads, system-linux-x86_64.ads, system-tru64.ads, 
	system-aix.ads, system-vxworks-sparcv9.ads, system-solaris-x86.ads, 
	system-irix-o32.ads, system-irix-n32.ads, system-hpux.ads, 
	system-vxworks-m68k.ads, system-linux-x86.ads, system-vxworks-mips.ads, 
	system-solaris-sparc.ads, system-solaris-sparcv9.ads, system-vms.ads, 
	system-mingw.ads, system-vms-zcx.ads, system-vxworks-ppc.ads, 
	system-vxworks-arm.ads, system-darwin-x86.ads, system.ads,
	system-vms_64.ads, system-darwin-ppc.ads, system-vxworks-x86.ads, 
	system-linux-ppc.ads, system-linux-hppa.ads, system-hpux-ia64.ads,
	system-vms-ia64.ads (Stack_Check_Limits): New target parameter.
	(Always_Compatible_Rep): New flag to control trampolines globally.
	(Dynamic_Trampolines_Used): New flag for implementing the
	No_Implicit_Dynamic_Code restriction more correctly (not yet used,
	and not yet set correctly for some targets).

	* s-taprop-vxworks.adb: Use stack limit method of stack checking.
	Simply indirectly call s-stchop when a task is created.

	* ali.ads: 
	New flag added: Stack_Check_Switch_Set which is set when '-fstack-check'
	appears as an argument (entries A) in an ALI file.

	* fe.h (Stack_Check_Limits): Declare new target parameter.
	(Check_Implicit_Dynamic_Code_Allowed): New procedure.

	* init.c: Declare __gnat_set_stack_limit_hook for VxWorks kernel RTS.
	This variable is declared in C to be sure not subject to elaboration
	code.
	(__gnat_map_signal, VxWorks): In kernel mode, map SIGILL to
	Storage_Error.

	* targparm.ads, targparm.adb (Stack_Check_Limits): New parameter.
	(Always_Compatible_Rep, Dynamic_Trampolines_Used): New parameters.

	* s-stchop.ads: Add comments.

	* s-stchop-vxworks.adb: Package almost fully rewritten to use stack
	limit method of stack checking.

	* s-stchop-limit.ads: New file.

From-SVN: r130814