update ngx/openresty annotations

[flrgh]

There's some new stuff in here:

• added type annotations for resty.core.regex
• added some new types/annotations to ngx

...but a lot of the work done was just boring cleanup:

• fixed many incorrect function return type annotations
• removed broken markdown links
• removed nonexistent ngx.* functions
• trimmed annotations for readability
  • removed extraneous empty lines
  • removed many This API was first enabled in the v0.9.9 release. types of notes (these are rarely helpful since OpenResty doesn't add new features very often, and they take up lots of screen real estate).

[sumneko]

Thank you!