Config option override

Just brainstorming again, on the subject of options flags starvation and other things.

How about adding an option --config-option=[[SECTION:]OPTION=VALUE[, ...]] that itself doesn't need any flag (we'd use FLG_ZERO which is actually 0, because we handle OPT_REQ_PARAM cleverly in Jumbo).

options.c would just prepare a struct list_main *cfg-cli with any options given. config.c would process that list after all and any files, and they'd override any config file settings.

We could then do things like --config-option=SingleRetestGuessed=no,SinglePrioResume=yes or --config-option=Opencl:ResumeWS=y and it would be just like putting those values in the config file.

Any existing features that use cfg_get_bool/int/param)() will now turn into possible command-line options and several existing command-line options could be deprecated (although they'd often be less easy to write).

Start by reading options.c and config.c, focusing on how command-line options and configuration files are currently processed. Trace the existing cfg_get_bool/int/param() uses and the OPT_REQ_PARAM handling in Jumbo. Done would mean a defined --config-option behavior that applies supplied values after configuration files and has tests or documented verification for the examples in the issue.