Update versions of opus and mpg123 libraries

[bemoody]

This pull request updates the version numbers for the built-in libraries (for MacOS and Linux builds) to their latest upstream versions:

• libopus 1.4 -> 1.5.2 (see https://www.opus-codec.org/downloads/)
• libmpg123 1.32.3 -> 1.32.6 (see https://www.mpg123.org/download.shtml)

The other version numbers in linux_build.sh and mac_build.sh appear to be up-to-date (however, the current MacOS arm64 binary is out of date.)

I haven't done any testing beyond checking that it compiles on Debian 12 amd64, and running the soundfile test suite.