We have ptrace defines and functions that are part of UAPI,
and we have some internal stuff not to be exposed. Split
ptrace.h into two files accordingly.

While at it, do some cleanups:
 - add ptrace_ prefix to some functions and macros
 - remove (duplicated) PTRACE_* defines from .c files
 - rename ptrace_seccomp(), remove its duplicate
 - remove unused ptrace defines
 - remove unneeded (ptrace-related) includes

travis-ci: success for compel uapi cleanups
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Reviewed-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>