Tie into the periodic function so we can get the APM info.
For now it's not checking that some time has elapsed, the hope
is that it'll just be driven by md_main_loop() / 5 second select
timeout.
Totally not ready for prod, but at least I'm making progress
figuring out how to add extra bits to this thing.
* add a second widget to the menu bar, next to the title bar
* add a new module command to update the battery information
* add a freebsd specific Battery module, not linked into the
build right now.
* amiwm will print out whenever we get battery information from the
module.
Right now I'm trying to figure out how to get some kind of periodic
background event into the module main loop. Launcher does it
using cx_broker(), but I dunno if I can adapt that pattern here.
