setting an undeclared variable results in a crash

[mschuldt]

variables need to be 'declared' with var before set can be used to set their value. this error should not result in a crash. And is the distinction between var and set really necessary?

'$ make run
gforth raillisp.fth
// Raillisp 0.1 \\

> (set x 4)
(set x 4) 

in file included from *the terminal*:0:-94508583085903: 
in file included from *the terminal*:-1:1: 
raillisp.fth:1606:36: error: Invalid memory address
s" _noinit_" find-name 0= s" init" >>>call-lisp<<< drop
Backtrace:
raillisp.fth:1477:64:                    0 $7F390FD166F0 execute 
raillisp.fth:1477:64:                    1 $7F390FD166F0 execute 
raillisp.fth:1605:18:                    2 $7F390FD1F2F8 
raillisp.fth:1605:18:                    3 $7F390FD1F5F0 
raillisp.fth:1334:35:                    4 $7F390FD14638 execute