This adds support in rustdoc to blanket apply crate attributes to all doc tests
for a crate at once. The syntax for doing this is:
#![doc(test(attr(...)))]
Each meta item in `...` will be applied to each doctest as a crate attribute.
cc #18199
All methods listed in "Trait Implementations" now hyperlink to the source trait
instead of themselves, allowing easy browsing of the documentation of a trait
method.
Closes#17476
This ensures that all external traits are run through the same filters that the
rest of the AST goes through, stripping hidden function as necessary.
Closes#13698
