Merge the following from the English version with some
corrections (blank line, rewrap, comment):

1.251 -> 1.286 handbook/pgpkeys/chapter.sgml

Submitted by: Hiroo Ono <hiroo _at_ jp dot FreeBSD dot org>
Reviewed by: Ryusuke Suzuki <ryusuke _at_ jp dot FreeBSD dot org>
References: [doc-jp-work 1767, 1985]