The new ConfKeyInfo structure now includes some fields indicating how
to load and save each config option: what keyword it's stored under in
the saved settings file, and what its default value should be set to
when loading a session that doesn't mention it. (Including, of course,
loading the null session at program startup.)
So far, this only applies to the saved settings that are sufficiently
simple: a single integer, string or boolean value whose internal
format matches its storage format, or an integer value consisting of a
finite enumeration with a fixed mapping between its internal and
storage formats. Anything more difficult than that - mappings,
variable defaults, config options tied together, options that still
support a legacy save format alongside the up-to-date one, things
under #ifdef - hasn't yet been tampered with.
This allows a large amount of repetitive code in settings.c to be
deleted, and replaced by simple loops over the conf_key_info array
doing all the easy work. The remaining manual load/save code per
option is all there because it's difficult in some way.
The transitional test_conf program still passes after this upheaval.
