This introduces new Deprecated:, Version Added:, and

Version Changed: sections for docstrings that allow for specifying

deprecation information, the version something was added, and the

version something was changed, respectively. These work like any other

doc sections, and wrap .. deprecated::, .. versionadded::, and

.. versionchanged::, taking the version number on the first line of

the section's body like a return type.

Used this in documentation and verified the output for each type.

Checked for build errors.