With this patch, it's now possible to pass a Gfx::ShareableBitmap in an
IPC message. As long as the message itself is synchronous, the bitmap
will be adopted by the receiving end, and disowned by the sender nicely
without any accounting effort like we've had to do in the past.
Use this in NotificationServer to allow sending arbitrary bitmaps as
icons instead of paths-to-icons.
We currently use icon paths for this because I didn't want to deal with
implementing icon bitmap sharing right now. In the future it would be
better to post a bitmap somehow instead of a path.
This patch adds NotificationServer, which runs as the "notify" user
and provides an IPC API for desktop notifications.
LibGUI gains the GUI::Notification class for showing notifications.
NotificationServer is spawned on demand and will unspawn after
dimissing all visible notifications. :^)
Finally, this also comes with a small /bin/notify utility.
