Delete term meta when deleting a term

[barryceelen]

When deleting a post or user its meta values are deleted as well. The patch adds the same behaviour when deleting a term via wp_delete_term().

[boonebgorges]

Welcome to Trac, and thanks very much for the patch, @barryceelen ! Let's get this into 4.4.

[boonebgorges]

In 35585:

When deleting a term, delete its metadata as well.

Props barryceelen.
Fixes #34626.

[swissspidy]

"Type of object metadata is for (e.g., comment, post, meta, or user)."

Meta is wrong, it should be term.

[barryceelen]

Fixes incorrect comment on delete_metadata_by_mid(), adds term meta code comment love to other meta functions

[boonebgorges]

Groan. Thanks, @swissspidy.

@barryceelen Thanks for the patch. To reduce churn, I'm going to leave these docblocks untouched. The description reads "e.g.", which means "for example". We don't need for the list to be comprehensive, and in fact, it can't be comprehensive since plugins can use these functions for custom metadata.

[boonebgorges]

In 35588:

Fix documentation typo introduced in [35585].

Props swissspidy, barryceelen.
See #34626.

[barryceelen]

@boonebgorges Sounds good + thanks for accepting my first patch!