Change default backend to hunspell.
aspell support is now a (disabled by default) option.
Add some other options.
Remove aspell from includes in buildlink3.mk. The backends
are abstracted into dynamically loaded modules and don't need
to be pulled in by buildlink3.mk.
Release notes:
Voikko (Finnish) language support. Zemberek (Turkish) language support.
Better support for Unicode in the personal dictionaries. Personal
dictionaries offer better suggestions. OpenOffice's dictionaries are used
on Windows. Aspell works on Windows. This release can use a system-wide
Hunspell/Myspell installation on Unix-like platforms. Hunspell 1.2.1 and
NET bindings are required. This release has more lax language matching
rules. It uses XDG's data-dirs spec for locating dictionaries. There are
many unit tests and bugfixes.
