This change added support "end of central directory record comemnt" to the Writer.

There is a new exported field Writer.Comment in this change.
If invalid size of comment was set, Close returns error without closing resources.

Fixes #21634

Change-Id: Ifb62bc6c7f81b9257ac83eb570ad9915de727f8c
Reviewed-on: https://go-review.googlesource.com/59310Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>