remove U_HAVE_STD_ATOMICS and similar @internal macros

Description

ICU 64+ no longer uses the U_HAVE_STD_ATOMICS macro, but we still have

and similar internal macros.

Remove obsolete macros marked as internal.

Assignee

Andy Heninger

Reporter

Markus Scherer

Components

Labels

None

Reviewer

None

Priority

medium

Time Needed

Minutes

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