compel: add per-arch handle-elf.c

Split handle_elf() function from main.c to per-arch.
Rename it to handle_binary not to cross-reference.
Rename generic handle_elf to __handle_elf as with define
not to litter namespace.

Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>