Orderless todo:

 - add option to recursively dump any struct inside requested struct
(only fill in padding or resue option to extract all members? figure
another syntax to specify substruct.field?)

 - add option to list all the structs available in a file

 - refactor some (in particular add wrappers/helpers around dwarf
functions so we abort properly checking both error and !ok, with
clear error messages)

 - log levels ?

 - pack elements into the same union member when sizes are appropriate
(need to be careful about embedded structs when we're not in recurse
mode? or have a mode that replaces 'em with char[x]?)

 - refactor to not print immediately but fill a tree, so we could get
rid of successive padding when elem size follows

 - Fix anonymous struct/unions (need some sort of recursivity; probably
depends intermediate representation)