- make control block to keep all information
   needed to run injected syscall and parasite
   blobs

 - add ptrace_swap_area helper

 - handle both parasite engine calls and injected
   syscalls by single __parasite_execute function

 - drop jerr() usage

 - bring back handling of inflight signals from
   original program inside parasite code
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>