wesley.craig@umich.edu did not document his previous KPOP patch, so I did so,

wesley.craig@umich.edu did not document his previous KPOP patch, so I did so,
and asked him to check what I wrote.  Unfortunately he didn't notice my
misunderstanding of his patch.  I wrote that if you #define POPSERVICE "kpop",
inc and msgchk will use KPOP exclusively, but if you leave it as "pop3", you can
use Wesley's new -kpop switch on a given invocation.  Instead, however, -kpop
turned out to be necessary on every invocation, and a KPOP user complained.
Applied Wesley's new patch, which makes things work like I thought his original
patch did.  After that, did one more clarifying pass to the documentation in
inc.man and msgchk.man.