[IDEA] New pages for types: structs and typedfefs

[Alejandro Colomar]

Here's a link to my branch where I'm developing system_data_types.7 and
the many link pages:

https://github.com/alejandro-colomar/man-pages/tree/system_data_types

I'll usually send an update to this thread from time to time, in the
form of a single commit, to ask for comments.

However, to find the latest version, and also see a detailed commit
history of the changes, you can follow that link.

Alex