Auto-link known functions, classes, and methods in the Code Reference

[DrewAPicture]

There has been discussion in the past about adding the ability to auto-link known functions, classes, and methods in the Code Reference to avoid littering inline @see tags throughout core docs. Let's make that happen.

[coffee2code]

In 2814:

developer.wordpress.org: Auto-link plaintext references to classes, functions, and methods.

• Ignores references made in <code> blocks.
• Does not attempt to recognize references to hooks. Such references must use {@see 'hook_name'} syntax.

Fixes #1483.