Overhaul Module API; fix debugging messages

Don't force Config debug message when trying to parse the module path in
main(). Just try to avoid giving the module path to Config.

Reintroduce 'steady modules' (formerly 'syms modules') which will be loaded
and then remain in memory. Currently, there's no way to later unload them
for memory reasons.

Use WARN() when different API version is detected. And detect the API
version correctly (dlsym returns a pointer to the symbol).

Remove 'Inserting module: ...' DEBUG statement.

insert_module() now takes a user pointer argument to give from one to the
next module.

I pulled event.h into this commit because it's referred to in module.c. I
think it will compile now but now execute. The rest will follow.