Unfortunately PHP does not provide any means to autoload the files that
a functions is located in, even if they are in an namespace.
To work around this, Composer makes use of an `autoload.files` section
in the `composer.json` file. Shortly after the Composer autoloader is
registered with the `spl_autoload_register` call it also includes any
files listed in this section.
Moodle does not do this and really we should be doing so.
This change adds a section to the autoloader registration method which
loads all of the files defined in any third-party library included in
our `lib` directory which contains any `composer.json` file with such a
stanza.
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