Sizes struct and Colordata simplified with clone? about libraw-rs

[gennyble]

Alright, that makes a lot of sense! I'll write the Colordata struct like Sizes, then.

[paolobarbolini]

Re-exporting structs from libraw-rs-sys could work for the simpler ones. I think the issue starts when we look at structs like libraw_data_t, which contain raw pointers, or libraw_processed_image_t, which contains C-like enums. These structs shouldn't be exposed to the user as-is, so for the sake of consistency I'm thinking we should probably avoid re-exporting any of the libraw-rs-sys structs from libraw-rs. This would also make them a bit easier to read, without having to think what types like ushort mean.