opt: add opt_log_stderr_exit helper, and opt_usage NULL option.
[ccan] / ccan / opt / _info
2010-10-07 Rusty Russellopt: fix example to compile.
2010-10-06 Rusty Russellopt: fix examples so they compile.
2010-09-29 Rusty Russellopt: new module to parse commandline options.