s390, s390x: use PTRACE_GETREGSET to fetch registers

* linux/s390/arch_regs.h: New file.
* linux/s390x/arch_regs.h: New file.
* Makefile.am (EXTRA_DIST): Add them.
* signal.c (sys_sigreturn) [S390 || S390X]: Use s390_frame_ptr.
* syscall.c [S390 || S390X] (s390_regset, s390_frame_ptr): New variable.
[S390 || S390X] (ARCH_REGS_FOR_GETREGSET): New macro.
(print_pc) [S390 || S390X]: Use s390_regset.
(get_scno) [S390 || S390X]: Likewise.
(get_syscall_args) [S390 || S390X]: Likewise.
(get_error) [S390 || S390X]: Likewise.
(get_syscall_result) [S390 || S390X]: Remove.
diff --git a/Makefile.am b/Makefile.am
index 587dd7a..589e61b 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -264,12 +264,14 @@
 	linux/powerpc64/syscallent1.h	\
 	linux/powerpc64/userent.h	\
 	linux/ptp_clock.h		\
+	linux/s390/arch_regs.h		\
 	linux/s390/ioctls_arch0.h	\
 	linux/s390/ioctls_inc0.h	\
 	linux/s390/syscallent.h		\
 	linux/s390/userent.h		\
 	linux/s390/userent0.h		\
 	linux/s390/userent1.h		\
+	linux/s390x/arch_regs.h		\
 	linux/s390x/ioctls_arch0.h	\
 	linux/s390x/ioctls_inc0.h	\
 	linux/s390x/syscallent.h	\