Minor updates
Getting rid of some output
Making sure to close the meld when turning a wall file into a meld file.
Avoiding lots of unnecessary writes to the header.

This saves an enormous amount of time writing files.  But it is essential that any
MeldWriter that is created gets *closed*.  Not sure if there is a way to automatically
catch problems with this.
Got rid of unused field 'cur' and one last unnecessary _write_header call