* automake.in (append_comments): New. Extracted from

* automake.in (append_comments): New.  Extracted from
read_am_file.  Match 'n' with a regexp, don't use substr (the
perlport man page says 'n' is not always one byte wide).
(read_am_file):  Use it.  Always chomp $_.
(file_contents_internal):  Use append_comments.
(macro_define): Don't treat the trailing 'n' with substr, use
a regexp or chomp.