The standard MyThes dictionaries include words that we don't support
(nearly half the entries in the English dictionary have speaces in them)
which waste space, and they aren't UTF-8 which slows down loading as we
need to convert them.
Knocks a total of 10 MB off the thesaurus dictionaries.
The list of files to include was out of date and only included files
for dependencies which were actually enabled, and the script was
FreeBSD-specific.
Originally committed to SVN as r6298.
