Working on guile-srfi-123.

Hello,

I am working on a Guile library for SRFI-123.

https://codeberg.org/kakafarm/guile-srfi-123/ or
https://kaka.farm/~stagit/guile-srfi-123/ if codeberg is down.

Currently I have removed the `cond-expand`s in the SRFI-123 example
implementation in `./srfi/srfi-123.scm`.  The example tests all pass.

I am also experimenting with an implementation in GOOPS in
`./srfi/srfi-123/goops.scm`.  Its tests do not pass.

I would appreciate any input whatsoever!