doc cleanup
allow alternate "no return" flags

If "no-return" is specified, the default tag for the non-returning
functions is "_Noreturn".  However, if the attribute is not the
empty string, that will be used instead.  And doc the stuff.
set release version
rework arg-optional

The description in the doc was not as clear as possible.
quote CFLAGS value

Thanks to Leo Davis --
* autoopts/tpl/usage.tlib: The values passed through the environment must be
  protected against shell tokenization.
* doc/autogen-texi.txt: fix description of generated main() proc.
* autoopts/tpl/getopt.tpl: declare optionUsage, too.
* autoopts/tpl/optmain.tlib: clean up main proc generation
* autoopts/test/getopt.test: adjust test

From more email:
* doc/auto_gen-tpl.in:  "directive" values are no longer extracted from
  agen5/defDirect.c.  Instead, sed out the documentation.
ChangeLog is now history
fix directive derivations

* doc/auto_gen-tpl.in: extract the directive information into files
  that can be alphabetically sorted.
* agen5/defDirect.c: all directives are now handled by specific
  functions, even always-fail and always-ignored directives.
* agen5/mk-stamps.sh: omit the #defines of ignored and handled-by-
  error directive functions.
* agen5/defLex.c(gather_name): correct skip-over-a-number code.
* agen5/test/debug.test: use the new, improved "'...'" quotes
  instead of the bad, old "``...''" quotes
LIBGUILE_PATH is not needed, but "tr" is

* autoopts/test/defs.in: remove the code that uses LIBGUILE_PATH
  and find the "tr" program
* config/confmacs.tlib: remove the code that tried to create
  LIBGUILE_PATH
* compat/compat.h: #defined values used in preprocessing expressions
  cannot be type cast
Version 5.18.2

final polish
copyright notice address

Change from Franklin Street to URL.
Also update fdl.texi