Added 'noduplicate' function attribute.
Added the 'sspstrong' function attribute
 and updated on-hover documentation for the 'ssp'-family attributes.
Updated function attribute groups format.
Added 'builtin' and 'nobuiltin' function attributes.
Updated sanitize attribute names and descriptions.
Added 'cold' function attribute.
Added the 'returned' parameter attribute.
Added 'optnone' function attribute.
Added support for function prefix data.