Module crossbeam_utils

Available on doc or test only.

crossbeam-utils modifications

(↑) This is derived work from the CachePadded struct in the crossbeam-utils crate, including the following modifications:

• rename to CacheAlign.
• add missing attributes.
• add fn into_inner_copy.
• add associated const ALIGN.
• feature-bound unsafe uses.
• misc. refactors.