file exists system predicate
$source_file -> $user source
hide and make system preds
fix check_head_and_body
user_expansion never fails
goal expansion is controlled b dynamic procedure
add must_be_of_type predicate_indicator
fix neat_call, debug flag is user controlled
use simplecudd, not ptoblogbdd
compile all of myddas
fx junk in file_name
fix warnings
use common file opening struct and funds
avoid pairs module
fix db queues
meta.yap contains meta-expansion
new mod.yap contains module declarations
module.yap keeps the rest.
undefcode refers to meta expansion
lots of annoying little errors.
