I was curious about this, too. Below is a dump of the API in JSON format. Unfortunately I don't think the same is available in XML format, or that the query can be further refined to, say, retrieve only a list of hooks.
URL structure:
api/(project)/full_list/(branch)?limit=M&page=N
https://api.drupal.org/api/drupal/full_list/7?limit=20&page=0
Source: Issue# 2369135: Public API into api.drupal.org?