FFI spec

[Simon Peyton-Jones]

Manuel

I've just had cause to look at the FFI spec.  Here's an idea.

Since we have two productions, one for foreign import and one 
for foreign export, let's separate the productions for "entity" into
"import_entity" and "export_entity".  That way we don't have to 
say "entity" in *both* 4.1 and 4.2.  

Would that be OK?  If so, would you like to action it.  This is 
for clarity only -- no change to semantics.

Simon