texinfo.tex doubled words, debugging lines doc buglets

[Karl Berry]

Should be only one "as":
% Use \ in index files by default.  texi2dvi didn't support @ as as the escape 

Should be only one "with":
% Finished with with double columns.


Also, the console messages:
  Writing index file eplain.fn
  ...
  trying to print index fn
seem like leftovers from debugging, especially the second. FWIW ... -k