collapseos/blk/391

2. Immediate words that have been cross compiled *cannot* be
   used. Only immediates from the host system can be used.
3. If an immediate word compiles words, it can only be words
   that are part of the stable ABI.

All of this is because when cross compiling, all atom ref-
erences are offsetted to the target system and are thus
unusable directly. For the same reason, any reference to a word
in the host system will obviously be wrong in the target
system. More details in B260.

These rules result in some practicals do's and dont's:

1. No LEAVE in DO..LOOP

                                                        (cont.)