Implement seccomp decoding

* configure.ac (AC_CHECK_HEADERS): Add linux/filter.h
and linux/seccomp.h.
* defs.h (print_seccomp_filter): New prototype.
* linux/dummy.h (sys_seccomp): Remove.
* linux/syscall.h (sys_seccomp): New prototype.
* prctl.c: Include <linux/seccomp.h>.
(sys_prctl): Decode PR_SET_SECCOMP.
* seccomp.c: New file.
* Makefile.am (strace_SOURCES): Add it.
* xlat/bpf_class.in: New file.
* xlat/bpf_miscop.in: Likewise.
* xlat/bpf_mode.in: Likewise.
* xlat/bpf_op_alu.in: Likewise.
* xlat/bpf_op_jmp.in: Likewise.
* xlat/bpf_rval.in: Likewise.
* xlat/bpf_size.in: Likewise.
* xlat/bpf_src.in: Likewise.
* xlat/seccomp_filter_flags.in: Likewise.
* xlat/seccomp_mode.in: Likewise.
* xlat/seccomp_ops.in: Likewise.
* xlat/seccomp_ret_action.in: Likewise.
diff --git a/linux/syscall.h b/linux/syscall.h
index ba585b3..45d261a 100644
--- a/linux/syscall.h
+++ b/linux/syscall.h
@@ -222,6 +222,7 @@
 int sys_sched_setaffinity();
 int sys_sched_setparam();
 int sys_sched_setscheduler();
+int sys_seccomp();
 int sys_select();
 int sys_semctl();
 int sys_semget();