[OS X Emacs] distinguishing various flavors of emacs in elisp

[Richard Cobbe]

I've been running an install of "Emacs for MacOS X" (apologies; not sure
what the technical name for this build is, but I mean the one from
http://emacsformacosx.com/), and I've recently switched to an AppKit build
of 23.3b that I did myself, with help from David Reiter and Peter Dyballa
-- see the thread late last month on this mailing list about displaying
Devanagari correctly.

I find that I need to adjust a couple of parameters in my .emacs file
slightly differently for the two builds -- most notably, line-spacing in
default-frame-alist.  What's the best way to distinguish between the two
builds in elisp?  Grepping for "AppKit" (as opposed to "appkit") in the
output of emacs-version?

Thanks,

Richard