Add: XCvar annotations to generate a menu

[Razish]

to allow producing a menu file based on xcvar parameters and embedding long names/descriptions for menu strings. hopefully we can do this all via pre-processor. We could take it one step further and have JA's preprocessor run through it at runtime so the cached menus don't lag behind, i.e. they're always up to date with the current code build, so no removed cvars end up in the menus.

may require some ui/cgame communication, not likely to require engine calls that screw over the syscall alignment.

[ensiform]

Not sure what you mean by this?

[Razish]

Producing a .menu at runtime via preprocessor magic for controlling cvars