* automake.in ($SUBST_REF_PATTERN): Do not define.

* automake.in ($SUBST_REF_PATTERN): Do not define.
(%gen_varname): Move to Variable.pm, as %_gen_varname.
(initialize_per_input): Do not clean %gen_varname.
(handle_options, check_libobjs_sources, handle_source_transform,
handle_LIBOBJS, handle_ltlibraries, handle_texinfo_helper,
handle_man_pages, handle_dist, handle_subdirs, handle_gettext,
am_install_var): Adjust to use value_as_list_recursive,
loc_and_value_as_list_recursive, and has_conditional_contents.
(require_file_with_macro): Accept an Automake::Variable as argument.
(traverse_variable_recursively,
traverse_variable_recursively_worker, gen_varname,
transform_variable_recursively): Move ...
* lib/Automake/Variable.pm (traverse_variable_recursively,
_traverse_variable_recursively_worker,
_gen_varname, transform_variable_recursively): ... here.
* automake.in (variable_conditionally_defined,
variable_value_as_list_recursive_worker,
variable_value_as_list_recursive
variable_loc_and_value_as_list_recursive): Move ...
* lib/Automake/Variable.pm (has_conditional_contents,
_value_as_list_recursive_worker,
value_as_list_recursive, loc_and_value_as_list_recursive): ... here.
(reset): Reset %_gen_varname.