I have submitted a pull request containing a second draft of
the SRFI specification, accompanied by complete (if somewhat
rough) sample implementations, a test program, and a kernel
benchmark.  As submitted, the sample implementations default
to kernel8; to switch to kernel0 or kernel16, change one line
in 135.sld.

The most important changes in the second draft are:

    Recommended an external representation for immutable texts,
    and used that representation to simplify the examples.

    Renamed procedures that accept both strings and texts to
    begin with "textual-" instead of "text-".

    Adopted John Cowan's proposed spec for conversions to and
    from UTF-8 and UTF-16.

    Changed textual-index and its three friends to return #f
    when no match is found.

    Added subsections on subtypes, recommended external
    representation, and Unicode.  Added a reference for
    Unicode.

    Adopted John Cowan's suggestion that textual-copy never
    share characters with its source text.

    Flushed textual-reverse.

Will