[support] Override Form API Theme Functions

[Fred Jones]

In a Drupal 6 site, I want to override theme_select but my
mymodule_select is never called. I tried instead making
mymodule_form_element because theme_select anyway calls that for its
output, but that custom function is also never called.

The reason, BTW, that I want to do this is to be able to apply a class
to some <option> tags.

Any ideas what I am doing wrong?

Thanks.