<PFE-SMART>
creates a set of interpret-words that are used in the inner
interpreter, so if a word is unknown to the interpreter-loop
it will use the first char of that word, attach it to an
"interpret-" prefix, and tries to use that IMMEDIATE-DEFER-word
on the rest of the word. This SMART-INTERPRET-INIT will set up
words like interpret-" so you can write
"hello" instead of " hello"
and it creates interpret-\ so that words like \if-unix are
ignoring the line if the word \if-unknown is unknown in itself.
This is usually not activated on startup.
reference: p4_smart_interpret_init in ../src/yours.c:0298, export CO SMART-INTERPRET-INIT