Add new header definitions from Linux 4.4 (plus older ptrace definitions).
This patch adds some new header definitions from Linux 4.4:
* MCL_ONFAULT is added to bits/mman.h / bits/mman-linux.h (this was
already done for hppa).
* PTRACE_SECCOMP_GET_FILTER is added to sys/ptrace.h. Along with it,
the older PTRACE_GETSIGMASK and PTRACE_SETSIGMASK, added in Linux
3.11 but missed at the time, are also added.
Tested for x86_64 and x86 (testsuite, and that installed stripped
shared libraries are unchanged by the patch).