MUL's application skeleton that they like us to use (and that saves
us work) sucks down all the command-line opts via getopt and doesn't
expose it to the application.  It also parses options before it
initializes the application "modules", so we can't supply a new app
callback to handle the opts.

Thus, we add what is basically a secondary initcall-like thing,
except this one is a struct of callbacks (including the per-app
getopt parsing function) and data (like the opts and longopts).  So
the macros define a section of per-module getopt parsing info
struct pointers, and before calling getopt, the skeleton main
expands its opts, longopts, and usage with info from these per-app
getopt helper info structs.

So it really is like a (very) poor man's argp.