Merge the following from the English version.
Note that an <link linkend="portsnap">...</link> is temporarily
commemted out due to a not-translated-yet part in
cutting-edge/chapter.sgml.

1.287 -> 1.289 handbook/ports/chapter.sgml

Submitted by: Ryusuke Suzuki <ryusuke _at_ jp dot FreeBSD dot org>
Reference: [doc-jp-work 1935-1937]