x86: Support shadow stack pointer in setjmp/longjmp

Save and restore shadow stack pointer in setjmp and longjmp to support
shadow stack in Intel CET.  Use feature_1 in tcbhead_t to check if
shadow stack is enabled before saving and restoring shadow stack pointer.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

	* sysdeps/i386/__longjmp.S: Include <jmp_buf-ssp.h>.
	(__longjmp): Restore shadow stack pointer if shadow stack is
	enabled, SHADOW_STACK_POINTER_OFFSET is defined and __longjmp
	isn't defined for __longjmp_cancel.
	* sysdeps/i386/bsd-_setjmp.S: Include <jmp_buf-ssp.h>.
	(_setjmp): Save shadow stack pointer if shadow stack is enabled
	and SHADOW_STACK_POINTER_OFFSET is defined.
	* sysdeps/i386/bsd-setjmp.S: Include <jmp_buf-ssp.h>.
	(setjmp): Save shadow stack pointer if shadow stack is enabled
	and SHADOW_STACK_POINTER_OFFSET is defined.
	* sysdeps/i386/setjmp.S: Include <jmp_buf-ssp.h>.
	(__sigsetjmp): Save shadow stack pointer if shadow stack is
	enabled and SHADOW_STACK_POINTER_OFFSET is defined.
	* sysdeps/unix/sysv/linux/i386/____longjmp_chk.S: Include
	<jmp_buf-ssp.h>.
	(____longjmp_chk): Restore shadow stack pointer if shadow stack
	is enabled and SHADOW_STACK_POINTER_OFFSET is defined.
	* sysdeps/unix/sysv/linux/x86/Makefile (gen-as-const-headers):
	Remove jmp_buf-ssp.sym.
	* sysdeps/unix/sysv/linux/x86_64/____longjmp_chk.S: Include
	<jmp_buf-ssp.h>.
	(____longjmp_chk): Restore shadow stack pointer if shadow stack
	is enabled and SHADOW_STACK_POINTER_OFFSET is defined.
	* sysdeps/x86/Makefile (gen-as-const-headers): Add
	jmp_buf-ssp.sym.
	* sysdeps/x86/jmp_buf-ssp.sym: New dummy file.
	* sysdeps/x86_64/__longjmp.S: Include <jmp_buf-ssp.h>.
	(__longjmp): Restore shadow stack pointer if shadow stack is
	enabled, SHADOW_STACK_POINTER_OFFSET is defined and __longjmp
	isn't defined for __longjmp_cancel.
	* sysdeps/x86_64/setjmp.S: Include <jmp_buf-ssp.h>.
	(__sigsetjmp): Save shadow stack pointer if shadow stack is
	enabled and SHADOW_STACK_POINTER_OFFSET is defined.