Broken and inconsistent links in rust/src/doc

[gstjepan2]

In rust/src/doc guide-* files have broken links to the rust book and its chapters.

I assume guide-unsafe.md should link to nomicon, tutorial.md,into.md, guide.md and all other guide-* to the main book.
However since there is an inconsistent behaviour in few files such that they link to the build books (websites), instead of the sources themselves, I don't know where should they link (source or build)

[jieyouxu]

Huh, these documents are really old, yeah some of their links are broken.