In 11, FORTH will be the default, and Lua will be built by default,
but users will have to do something to use it. 12, both FORTH and Lua will
be built and installed, with Lua as default (barring unforeseen
complications). Once the co-existence stuff goes in, I imagine we'll make
the switch to Lua by default shortly after that. In 13, FORTH will be
removed unless there's a really really compelling case made to keep it.