Tools > Export does not include termmeta data for post categories

[jadpm]

Steps to reproduce

• Populate some posts and categories on a clean WordPress installation.
• Add some term meta fields to those categories.
• Go to Tools > Export and export Posts, then All categories.
• The export file contains no wp:category entry for any categories, hence categories term meta fields are not included.
• Go back to Tools > Export and export Posts, then a single category.
• The new export file contains no wp:category entry for the selected category, hence its term meta fields are not included either.

[jadpm]

Edit: the ticket description contains an error. When exporting Posts within a single category, its category term meta is indeed included int he export file.

For the record: the problem only affects exporting all categories for posts.

[jadpm]

Edit II: IMHO, we should also include tags and any custom taxonomy assigned to posts when exporting them. I will be providing a patch doing that.