[9fans] support for more dictionary files

[mirtchov@cpsc.ucalgary.ca]

I've added support for dictd (http://www.dict.org) files to dict(7).
There is a large amount of small dictionary files for many european
languages available too.  They are too small and incomplete in their
current form, however more complete entries are floating on the net,
converted to dictd format from various other electronic sources
(example of that is the bulgarian dictionary there).  I've provided
information on how to convert dictd files to be used with a dict(7)
which is patched to understand these flat files.

all required information is at:

	http://pages.cpsc.ucalgary.ca/~mirtchov/p9/dict/

The code also fixes a small bug with mkfile in /sys/src/cmd/dict which
leaves a dangling mkindex after a 'mk clean', which is then
distributed through sources.cs...  The file right now is compiled for
MIPS :)

Russ, the changes to the dict source are non-intrusive.  If there's no
objection can you include them to the default dict from Bell Labs?  I
will take care with the distribution of the actual dictionaries that I
support (bg/en and en/bg).  The other dictionaries are not (and need
not be) included for now -- until somebody finds a relatively complete
entry for their language of choice :)

andrey