Attached is a second patch.

* Now includes input and output checksums.  Checksums are now
  truncated to 16 characters each, otherwise the line is >80 columns.

* Fixes the doubled-up signature lines for type object slot default
  signatures.  I ran "gcc -E" and wrote a quick script to print out
  all lines with doubled-up signatures.  There were only two: divmod
  and rdivmod.

* Pretty sure this was in the first patch, but just thought I'd mention
  it: for functions using optional groups, we can't generate a legal
  signature.  So Clinic kicks out the name of the function instead
  of "sig=", meaning that it puts back the docstring first line
  for human consumption!  I am so clever, tee hee.