[release-branch.go1.20] net/mail: permit more characters in mail headers
We parse mail messages using net/textproto. For #53188, we tightened
up the bytes permitted by net/textproto to match RFC 7230.
However, this package uses RFC 5322 which is more permissive.
Restore the permisiveness we used to have, so that older code
continues to work.
For #58862
For #60332
Fixes #60874
Fixes #60875
Change-Id: I5437f5e18a756f6ca61c13c4d8ba727be73eff9a
Reviewed-on: https://go-review.googlesource.com/c/go/+/504881
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@google.com> Reviewed-by: Damien Neil <dneil@google.com>