[LITMUS^RT] Plugin tutorial updated

[Björn Brandenburg]

FYI: I've updated the "how to create a plugin" tutorial to the latest version.

	https://wiki.litmus-rt.org/litmus/CreateAPluginTutorial

The corresponding branch on Github has also been updated.

	https://github.com/LITMUS-RT/litmus-rt/commits/wiki-tutorial

There's now also a new Step 9 that covers interfacing with Glenn's /proc migration support.

	https://wiki.litmus-rt.org/litmus/CreateAPluginTutorial/Step9

Glenn, please correct any misconceptions on my part, and perhaps you can add a bit more detail to the description...

Thanks,
Björn