Add another wide_node temp creation function

Sometimes I want to creat temporary nodes with a manually specified
width.
Add DEBUG_OPERATION_ADDING #define

This prints every operation right before it goes out to libflo to be
merge into the main Flo file, which is useful for debugging width
inference failures.
Fix SUB op narrowing width bugs

I had a bunch of comparison operations in the SUB operation narrowing
that I was using the wrong destination widths for.  I hadn't noticied
this before because libflo was ignoring these widths, but
libflo-0.0.15 checks them and fails.

The fix is to just use the correct output width!