Jimmy-
As to the article itself, I think [[XFree86 logfile]] is very much a proper topic for an article in Wikipedia.
For me, one important question in deciding whether something belongs on Wikipedia is:
Does this article have the potential to ever become a featured article?
By that I don't mean that we shouldn't cover obscure subjects -- plenty of articles about obscure subjects have become featured articles. I mean that articles should have the potential to grow into a coherent, independent work that speaks for itself.
I am not very fond of articles that are destined to always remain stubs. I believe such articles would be more appropriately merged into larger pages (with redirects), or in some cases, deleted or moved to another Wikimedia project. I think doing so also helps our credibility when we boast about our article count.
Another test is whether an article is primarily *descriptive* or primarily *instructive*. If it is more of a how-to, it's probably best to put it on Wikibooks.
Applying these two tests to the articles in question I find: 1) The XFree86 logfile is a very complex subject that probably deserves its own article instead of being merged into [[XFree 86]]. 2) The OpenGL subroutine articles should probably be merged and redirected to [[OpenGL]]. 3) /var/log/wtmp should probably be merged and redirected to [[Filesystem Hierarchy Standard]] 4) Individual X modules should be described on [[XFree86]] at first, and only moved out if they get too long.
All articles are borderline in terms of the descriptive/instructive distinction. I think in such cases we can leave it to the original author to decide whether they work on a Wikibook or on the encyclopedia. By leaving this to the author, we also create an incentive for people who want it to be moved to Wikibooks to be nicer to the author. ;-)
Regards,
Erik