inotify.7: Add example program

This example of the usage of the inotify API shows the
usage of inotify_init1(2) and inotify_add_watch(2) as well
as polling and reading from the inotify file descriptor.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
inotify.7: Minor changes to Heinrich Schuechardt's example program

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>