* README.gpgconf (NAME): Add info about optional arg and arg type 0.
* gpgconf-comp.c (gc_component_change_options): Parse list of
arg type 0 options.
(option_check_validity): Add new argument NEW_VALUE_NR. Perform
rigorous validity checks.
(change_options_program): Disable an option also if we have a new
value for it.
* README.gpgconf: Revert last change. Add new flags "default",
"default desc" and "no arg desc". Add new field ARGDEF. Add new
field FLAG to backend interface.
* gpgconf-comp.c (struct gc_option): Make flags of type unsigned
long.
(gc_component_list_options): Adjust type for flags.
Add default argument field.
(retrieve_options_from_program): Use "1" as value for non-option
arguments, not "Y".
(gc_component_change_options): Read in flags from input.
