RE: datatypes in Elisp Info: mention "things" for which there is no "thing" datatype - e.g. faces

[Drew Adams]

    while i agree that the documentation could make more distinction between
    fundamental and composed (or "defined-by-conventional-use") types, i
    figure that doing so might be a bad idea because it would constrain the
    implementation.

    since `facep' works like `functionp' (fsvo "like"), that should be what
    programmers rely on.  if in the future faces become fundamental, that
    transition will be easier to handle if prior internals were left
    unexposed (ignorance is bliss).

One of my concerns is that readers of the datatypes section will not know
that faces exist. This section is near the beginning of the manual, and it
can give the impression that it also presents all of the important
Emacs-Lisp objects.

At a minimum, I think it would help to mention that, although these are the
only datatypes, there are additional things of interest (like faces) that
are not listed here.