Fix RTAI kernel detection for newer RTAIs

The ShabbyX repo, and probably RTAI 4.0, don't have the rt_daemonize
symbol in the i-pipe patch that older versions did.

This patch recognizes newer RTAI kernels by keying off of
rtai_irq_handler as well.
Merge pull request #186 from zultron/mk-pull

Fix RTAI kernel detection for newer RTAIs