Correctly parse node-attached widths

I was missing a "++" after a strstr.
Actually parse constant widths

I'd split the constant into two parts, the node nameand the width, in
order to attempt a node lookup.  I was accidentally passing just the
node name to the constant generation function instead of both, causing
constants to always be of unknown width.
Output the new Flo format

This matches the format that started to be parsed by

e3f919d Parse the output of the latest Chisel
Use new LSH, RSH semantics

It appears that the new Flo file format doesn't out information for
LSH because apparently it's not necessary -- I guess as long as all
constant widths are known then you're OK.

This is, unfortunately, not going to be strictly backwards-compatible
as it requires some previously-valid Flo files to have more
information in order to be valid.