Log Message:
libidn2: update to 2.3.7.

* Noteworthy changes in release 2.3.7 (2024-01-27) [stable]

** Really include tests/standalone.sh in tarball.

* Noteworthy changes in release 2.3.6 (2024-01-27) [stable]

** Bump libtool version numbers to reflect API/ABI addition.

** Include tests/standalone.sh in tarball.

* Noteworthy changes in release 2.3.5 (2024-01-27) [stable]

** Declaration of future API/ABI backwards compatibility stability.
GNU libc dlopen libidn2 and use the name libidn2.so.0 for this.  We
believe that it will be too challenging to ever do hard ABI break that
for normal libraries is justified to remove deprecated APIs.  Thus we
decided that we will support the current ABI for a long time.  Of
course, if really convincing arguments for doing a ABI break appears
in the future we may re-consider, but take this as a declaration of
intent of will and that future ABI breaks should be discussed and
co-ordinated with the glibc team first.

** Add public APIs for raw Punycode encoding/decoding.
Normal applications rarely need this, but it cleans up the code and
allow for external testing of the APIs, and resolve
<https://gitlab.com/libidn/libidn2/-/issues/80> due to earlier use of
weak symbols for internal symbols _idn2_punycode_encode and
_idn2_punycode_decode.  We will support these internal symbols for
backwards compatibility.  This allows a clean migration path for code
that is still using the internal names.

** Bump required gettext version to 0.19.8 for musl-libc.
Reported by Helmut Grohne in
<https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=999510>.

** Un-deprecate idn2_to_ascii_4i and make it NUL terminate output.
The API idn2_to_ascii_4i was deprecated in version 2.1.1 released in
2019-02-08.  In that release, the API was also modified to not
NUL-terminate the output.  That is contrary to the old libidn2
behaviour, the behaviour of libidn's API idna_to_ascii_4i, and the API
documentation for the function.  Since we are not likely to ever break
backwards API/ABI compatibility in libidn2, and the deprecated gaurds
leads to some trouble (see report in
<https://gitlab.com/libidn/libidn2/-/merge_requests/93>) we decided to
un-deprecate this function, as supporting it is not costly and the
majority of code that cares about conformance has likely been
modified.  This will fix the error code and NUL termination report by
Yegor Bychin in <https://gitlab.com/libidn/libidn2/-/issues/100>.  We
still encourage you to use the replacement API/ABI idn2_to_ascii_4i2
instead, when appropriate.

** Compiler warning improvements.
As before, compiler warnings are enabled by default.  You may disable
them using ./configure --disable-gcc-warnings or turn them into fatal
errors using ./configure --enable-gcc-warnings=error to add -Werror
and sensible -Wno-error='s.  Based on gnulib's manywarnings, see
<https://www.gnu.org/software/gnulib//manual/html_node/manywarnings.html>.

** tests: Added script tests/standalone.sh suitable for integrators.
The main purpose is to test a system-installed libidn2 library and
idn2 tool, suitable for distributor checking (a'la Debian's
autopkgtest/debci).  It may also be used to test a newly built libidn2
outside the usual 'make check' infrastructure.  To check that your
system libidn2 library and idn2 tool is working, invoke the script
with `srcdir` as an environment variable indicating where it can be
find the source code for libidn2's tests/ directory (it will use the
directory name where the script is by default):

tests/standalone.sh

If your system libidn2 is too old to pass certain tests, disable them
using STANDALONE_DISABLE like this:

STANDALONE_DISABLE='*punycode*' tests/standalone.sh

See the script for more parameters.  If the libidn2 under testing is
too old and has known bugs, that should cause tests to fail, which is
intentional.

** Various minor build fixes and translation updates.

** API and ABI is backwards compatible with the previous version.
idn2_punycode_decode: ADD.
idn2_punycode_encode: ADD.