Re-enable skipping duplicate hooks when parsing

[DrewAPicture]

Background

In mid-December 2014, the logic that skips parsing duplicate hooks in WP-Parser was ​disabled. WordPress core relies on skipping those duplicates so that references don't get overwritten with the "This action|filter is documented in ..." phrase instead of the intended hook doc.

It was pointed out this morning by @adamsilverstein, that some references were overwritten with the duplicate comment when we re-parsed for 4.1 at the end of the year. For instance: ​https://developer.wordpress.org/reference/hooks/_wp_post_revision_field_field/

Next Steps

In response to Adam's feedback, I ​added a new filter to WP-Parser to allow us to re-enable skipping of duplicate hooks when parsing: wp_parser_skip_duplicate_hooks.

Patch attached for the devhub theme.

[coffee2code]

In 1503:

developer.wordpress.org: Re-enable skipping duplicate hooks when parsing (prevents overwriting docs for primary instance).

Fixes #914.
Props DrewAPicture.