Log Message:
textproc/guile-json: Update to 4.1.0

* Version 4.1.0 (Jun 6, 2020)

  - Speed up number parsing by a 2x factor by avoiding using textual ports.

  - Simplify unicode string builder.

  - Improve string builder performance by not going back and forth with lists,
    strings and characters.

* Version 4.0.1 (May 17, 2020)

  - (scm->json-string) #:validate keyword argument should default to true as
    stated in the documentation.

* Version 4.0.0 (May 16, 2020)

Breaking changes:

  - (scm->json) and (scm->json-string) #:espace keyword argument has been
    renamed to #:solidus.

  - JSON null now defaults to the null symbol. This can be changed in all
    public functions with the #:null keyword argument.

Bug fixes and improvements:

  - Fix parsing of invalid numbers (e.g. "-").

  - Go back to using (cond) instead of (match) since (match) reduces
    performance.

  - The json-parser record type has been removed as the record only contained
    the port. Removing the need to access records also had a slight
    performance increase.

  - Use a plain list to read strings which brings significant speed
    improvements.

  - Replace `display` with `put-string` on JSON builder.

  - Don't use map to parse expected string, simply use (string-ref).
    (thanks to Linus Björnstam)

  - Build array list with (cons) and (reverse). Big performance increase.
    (suggested by Linus Björnstam)

  - Check (eof-object?) last instead of first. This avoids unnecessary checks
    which is the regular use-case.
    (suggested by Linus Björnstam)

  - Use string ports to parse numbers.
    (suggested by Linus Björnstam)

  - Don't need to use character-sets to detect whitespaces. JSON only defines
    four possible types of whitespaces: space, linefeed, carriage return and
    horizontal tab.
    (suggested by Linus Björnstam)

* Version 3.5.0 (Apr 21, 2020)

  - Simplify parser by using `match`. Idea taken from Chickadee's JSON parser
    (https://dthompson.us/projects/chickadee.html). This also made it easier
    to clean up some functions.

  - Better handling of invalid numbers.

  - Improve handling of EOF. Most parsing functions were not taking care of
    it.

  - Fix error when parsing objects with commas and no following elements are
    found.

* Version 3.4.0 (Apr 11, 2020)

  - Fix parsing 0 with an exponent.
    (Fixes #55)

  - Fix cross compilation.
    (thanks to Jan Nieuwenhuizen)