#4 eengine -pretty handling of NULL statements

[Thomas R. Thurman]

pretty option replaces a NULL statement
(e.g., "; --xxx")
with literal
" NULL;"
that is an invalid statement.
result is the compare between original and pretty printed fails.

for real example see AIM rule validate_dependently_instantiable_entity_data_types,
line prior to this line:
number_of_input_instances := SIZEOF(all_instances);