In the beginning of Collapse OS' Forth version, the readline sub-
system was optional. This is why we had this separate RDLN$ routine
and that the input buffer was allocated at boot time.

It's been a while since the RDLN system has been made mandatory, but
we still paid the complexity tax of this separation. Not anymore.

I wanted to make CVM's forth use the Grid subsystem, but doing so
would break the stage binary. Hence, this split.

I've noticed that under certain conditions, such as a stack overflow,
I would segfault, something I though was impossible because my memory
size is 0x10000 and all my integer variables are uint16_t.

After having re-read my C handbook, it seems I wasn't sufficiently
knowledgeable about type conversion rules.

They were a bit terse.

This will soon replace the libz80 based "forth" and
"stage" executables. This is much, much faster.