pipesz: add the pipesz utility

pipesz: add the pipesz utility

pipesz is a utility to examine and adjust the size of pipe buffers.

It uses fctnl F_GETPIPE_SZ and F_SETPIPE_SZ to examine and resize
these buffers. This functionality is unique to Linux and was added in
version 2.6.35. Minor bugfixes were made in 4.9, but these do not
obviate the use of pipesz prior to that release.

Signed-off-by: Nathan Sharp <nwsharp@live.com>
Signed-off-by: Karel Zak <kzak@redhat.com>