Log Message:
Use INFO_FILES for registering the mjpeg-howto.info documentation files.
And remove from PLIST.
This fixes problem when INFO_DIR is using a custom directory such
as share/info.

Do not bump PKGREVISION, because couldn't package in first place when
this problem occurred.

This will cause a warning:
install-info: warning: no info dir entry in `/usr/pkg/share/info/mjpeg-howto.info'
TODO: so add a START-INFO-DIR-ENTRY/END-INFO-DIR-ENTRY pair dir entry.