[R6RS] various issues

[dyb at cs.indiana.edu]

There are a few issues that I have found and didn't feel comfortable
fixing myself while proofreading:

  - need to fix the lex.tex description of termination for identifiers
    numbers, characters, and booleans.  (see my earlier mail and Mike's
    response.)

  - the set of <string element>s seems to be incomplete; Section 3.2.6
    lists also \x<digit 16>+; and \<linefeed> and \<space>.

    also, why does the set of <string element>s explicitly include <linefeed>
    and <intra-line whitespace>.  Don't they already fall into the
    <any character other than " or \> category?

  - we agreed that with (quote obj) and (datum->syntax id obj), an
    exception *should* be raised if obj is not a datum.  I think it
    now reads effectively as *must*.

  - with the textheight specified in r6rs, the first-page footnote is cut
    off on US letter-size paper.  you should see this reflected in the
    draft that I sent to the steering committee.

Kent