page-pipe/page-xfer: remove PP_COMPAT (compatible iovs)

Parasite transfers pages in the same iovec format now: drop compatible
format (yay!).

travis-ci: success for Rectify 32-bit compatible C/R on x86
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>