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'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.
