my-eproject.el/my-c-mode.el: clean-up setting of style

You can't set C style until C mode is running so you need to do it in
the hook. Fortunately you can just embed the c-style in the project
definition and add a hook. I tweaked my old school C style guesser to
fail gracefully so the two methods don't fight.

I should probably set default style now I no longer have mmm-mode about.