Go1.16 stdlib test fixes: sync/atomic, io, internal/unsafeheader, `internal/fmtsort`, and type assertion errors.#1004

Merged

nevkontakte merged 8 commits intogopherjs:go1.16-stdlibfrom

nevkontakte:go1.16-stdlib

Mar 22, 2021

Commits on Mar 21, 2021

Skip an `io` package test that fails due to a GopherJS compiler bug.
nevkontakte
committed
Skip an irrelevant `sync/atomic` test that was added in Go 1.16.
nevkontakte
committed

Commits on Mar 22, 2021