Please use individual XML files to get a good order for extensions

[rrthomas]

The Shared MIME-info Database spec says:

The first glob element represents the "main" extension for the file type. While this doesn’t affect the
mimetype matching algorithm, this information can be useful when a single main extension is needed
for a mimetype, for instance so that applications can choose an appropriate extension when saving a
file.

This is useful information. In particular, it would be good if the extensions() function returned the glob elements in the order defined in each file. The trouble is that the order is randomized in the globs file, if the weights are equal, so for example on my system the extension returned by extensions() in scalar context for applicaton/javascript is .jsm, and not the more obvious .js, which is the first in the XML file, and hence the main extension according to the spec.