This patch adds a simple GMessageBox that can run in a nested event loop.
Here's how you use it:
GMessageBox box("Message text here", "Message window title");
int result = box.exec();
The next step is to make the WindowServer respect the modality flag of
these windows and prevent interaction with other windows in the same
process until the modal window has been closed.
In order to move the WindowServer to userspace, I have to eliminate its
dependence on system call facilities. The communication channel with each
client needs to be message-based in both directions.
