add new PTRACE_SECCOMP_GET_FILTER ptrace command

allows the tracer to dump the bpf seccomp filters of the tracee,
new in linux v4.4, commit f8e529ed941ba2bbcbf310b575d968159ce7e895

include/sys/ptrace.h

@@ -39,6 +39,7 @@ extern "C" {
 #define PTRACE_PEEKSIGINFO 0x4209
 #define PTRACE_GETSIGMASK 0x420a
 #define PTRACE_SETSIGMASK 0x420b
+#define PTRACE_SECCOMP_GET_FILTER 0x420c
 
 #define PT_READ_I PTRACE_PEEKTEXT
 #define PT_READ_D PTRACE_PEEKDATA