Refresh file view when folder updates using inotify API

[apprehensions]

Linux provides an API for file changes called inotify, xfiles can use this API to refresh or reload the file view for new changes in the folder.

[rhaberkorn]

Should be optional, though as xfiles should continue to compile on all UNIX platforms. (FreeBSD for instance has a different Kevent-based API, but provides a libinotify in its ports tree.)

At the very least however, you should add a refresh (changedir ".") to xfilesctl after all operations that expect to change the directory contents.