Calculate .len of labels automatically

[hlorenzi]

I recently added #define sizeof(Begin) (pc - Begin)*2 so that I can get the size in bytes of a data region as a constant and it has become an extremely useful feature:

args:
#d16    1, 2, 3, 4, 5
.size = sizeof(args)

mov t0, args.size

Are there any ways to do something like that?

Originally posted by @p-rivero in #68 (comment)