Bootstrapped and tested on x86_64-linux with no regressions.

Finally, the fabled diagnostics patch. I would like to note really
quickly that there was never a v2 and v3 of this patch, only the first
of these 2 had those versions. Originally I had planned to revise this
patch alongside the first but it just didn't happen. Anyhow, I decided
to match the version of this second patch to the current first patch to
avoid any confusion. 

With that out of the way, I feel mostly okay about the code in this
patch, but I have a feeling it will need a revision, especially with
the large amounts of comments I left in. At the very least I expect to
need to pull those out before the patch can be accepted.

I had wanted to write about some of my frustrations with trying to
write a test for virtual specifiers and errors/warnings for
shadowing/overloading virtual functions, but I am a bit too tired at
the moment and I don't want to delay getting this up for another night.
In short, the standard does not properly specify the criteria for
overriding functions, which leaves a lot of ambiguity in how exactly we
should be handling these cases. The standard also really poorly
specifies things related to the implicit object parameter and implicit
object argument which also causes some trouble. Anyhow, for the time
being I am not including my test for diagnostics related to a virtual
specifier on xobj member functions. I can't get it to a point I am
happy with it and I think there will need to be some discussion on how
exactly we want to handle that.

I was fairly lazy with the changelog and commit message in this patch
as I expect to need to do another round on this patch before it can be
accepted. One specific question I have is whether I should be listing
out all the diagnostics that were added to a function. For the cases
where there were only one diagnostic added I stated it, but for
grokdeclarator which has the majority of the diagnostics I did not. I
welcome input here, really I request it, because the changelogs are
still fairly difficult for me to write. Hell, the commit messages are
hard to write, I feel I went overboard on the first patch but I guess
it's a fairly large patch so maybe it's alright? Again, I am looking
for feedback here if anyone is willing to provide it.

I've written more than I want here, so I'll wrap this e-mail up and go
to bed. I am very happy to be getting close to a final product here.
Hopefully if all goes well I'll be able to fit in the final missing
features before feature lock hits.

Alex