Synchronize documentation of the pyfits.info 'convenience' function with that of HDUList.info, which it wraps.  Specifically, pyfits.info's documentation did not mention the output=False option.

git-svn-id: http://svn6.assembla.com/svn/pyfits/branches/3.0-stable@2223 ed100bfc-0583-0410-97f2-c26b58777a21