Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.Approved by: re (implicit)Sponsored by: The FreeBSD Foundation
Use PC Card instead of other variants in the driver man pages.
Fixed cross references to pccbb(4), fixed spelling of "device cbb",and linked the pccbb(4) manpage to cbb(4).Reviewed by: imp
mdoc(7) police: Nits.
Explain what exca is.