Log Message:
Update autogen to 5.6.4.

AutoOpts:
* The listing of enumerated option arguments is a bit more concise.
* Options may be handled twice: once during the immediate phase and
  again during the "normal" processing phase.
* If environment variable "rc" processing is enabled, then the
  "${PROGNAME}" environment variable will be processed - tokenizing it
  and processing it as a list of command line options.  It may not
  contain any command line operands.
* a new main procedure type:  each-or-stdin  This will fopen() each
  command line operand and pass the FILE* pointer to the callout procedure.
  If there are no operands, then stdin is passed.
* main() procedures can be specified more consistently

AutoGen:
* The '$$' expansion in locating the program will now use "realpath(3C)".
  This way, if a program is installed in /opt/whatever/bin/program
  and you run it via a symlink, '$$' will resolve to /opt/whatever/bin.
* exist and not-exist selection macros -- the CASE macro can now
  select a clause based on value existence.  Previously, you could detect
  an empty string and you then had to use the ``(exist? "name")'' function.
* fixed tpl-file-line so that "%2$d" works for the format.
* Added (emit) function that directly emits its args into output
* keyword lists are columnized in usage text
* distributed subdirectories no longer depend on also being built.

getdefs (an AutoGen support utility):
* With "listed" attributes, if you quote an entry, then the scanning code
  has to push the scan forward to the next entry so we don't wind up with
  a spurious empty entry!!