Log Message:
Update autogen to 5.5.3.

Changes since 5.5.2 include:
* AutoOpts' usage procedure has been enhanced to produce either AutoOpts
  standard usage or usage that looks more like current GNU practices.
  The latter provides less information and help.
* I32LPx behavior has improved.  Don't think I can call it "industrial
  strength" just yet, tho.