docs/84639: pcm.4, handbook - note that vchan settings can't be changed while device in use

[Simon L. Nielsen]

Synopsis: pcm.4, handbook - note that vchan settings can't be changed while device in use

Responsible-Changed-From-To: freebsd-doc->simon
Responsible-Changed-By: simon
Responsible-Changed-When: Tue Aug 9 18:53:23 GMT 2005
Responsible-Changed-Why: 
Looks like it close a doc PR day, grab this one as well :-).

http://www.freebsd.org/cgi/query-pr.cgi?pr=84639