inception - parse comments in doc tests

[drahnr]

Summary

//! a doc comment
//! ```rust
//! /// currently this is not checked, can contain garbage
//! fn y() -> usize { 2usize }
//! ```


// I am ok!
struct Foo;

the inner documentation comments should also be checked as separate entity, as if the doc-test was a separate file.

Skeptic uses cmark just as we do, and the simplest approach would be to re-inject code blocks into the pipeline as virtual files.