Cleaned up some sloppy code (not initializing variables) that was
causing errors.

There are a bunch of places I do something like
sexp retval;
...
retval.tag=_cons;
retval.val.cons=...;
return retval;

and in general this hasn't really been an issue (for some reason). But I
reall should have done
sexp retval={0};
...
So all the meta data gets set properly (i.e. quote,comma,length,etc).

I cleaned up a few instances of this in the parser and changed the
foo_sexp macros to set any unused field to 0 and this fixed things, but
I should make sure to fix any other instances of this. I wager this was
what was causing other compiliers to fail.