It contained definitions for F_{SET,GET}PIPE_SZ, which
we already have in "fcntl.h" - it's not big, can be included instead.
Also it has pipe-size specific definitions, which are used only
in page-pipe.c -- moved them to page-pipe.h.

This will simplify include for config.h from subprojects.

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