Log Message:
lang/ecl: update to ecl-23.9.9

Tested by building and using math/maxima.

Release announcement:

ECL 23.9.9 release

Dear Community,

We are happy to announce a new stable ECL release tagged 23.9.9.
The new release includes many bug fixes, some new features,
improvements to the compiler and more. Changes include but are
not limited to:

 *  Complete overhaul of thread synchronization primitives (mutexes,
    condition variables, etc.). Users of bordeaux-threads will have
    to update as this breaks workarounds for missing timeouts on
    condition variable wait operations in version 0.9.1 and earlier
    of this library.
 *  Better unicode support: add new functions to convert between
    Lisp strings and byte arrays in different encodings, allow
    non-ascii characters in pathnames and as arguments to
    ext:run-program.
 *  Preliminary support for the Emscripten target (bytecodes
    compiler only).
 *  Various bug fixes and internal improvements to the compiler.
 *  Better conformance to the ANSI standard.

We'd like to thank all people who contributed to ECL with code,
testing, issue reports and otherwise.

People listed here contributed code in this iteration: Caleb Xu,
Catherine Tower, Daniel Kochmański, Dima Pasechnik, Dmitry
Solomennikov, Eric Timmons, Florian Margaine, Jeronimo Pellegrini,
Kevin Zheng, Kirill A. Korinsky, Marius Gerbershagen, Nick Faro,
Tarn W. Burton, Ulrich Müller, Yuguo Zhang, Yuri D. Lensky.

People listed here tested ECL extensively before the release:
Kirill A. Korinsky, Marius Gerbershagen and Paul Ruetz.

This release is available for download in a form of a source code
archive (we do not ship prebuilt binaries):

    ECL 23.9.9 tarball archive
    The ECL Manual

Happy Hacking,
The ECL Developers