Auto merge of #3490 - alexcrichton:dev-dep-doc-test, r=brson

Fix cargo test --doc with dev-deps

Previously Cargo accidentally didn't pull in dev-dependencies due to the way
`cargo test --doc` was interpreted in terms of top-level targets. This PR
special cases this situation by ensuring that the doctest intention makes its
way all to the backend and the dependencies can be correctly calculated.

Closes #3422

diff --cc src/cargo/core/workspace.rs
Simple merge

diff --cc src/cargo/ops/cargo_compile.rs
Simple merge

diff --cc src/cargo/ops/cargo_rustc/context.rs
Simple merge

diff --cc src/cargo/ops/cargo_rustc/mod.rs
index 4bcf363df19189efe74073f6eceb4139cd08bccd,0c9ea9decb262b0d29647ec8adcc59a7384298d3..162f985095e263e20381f5448f2412cfa290f0ce
--- 1/src/cargo/ops/cargo_rustc/mod.rs
--- 2/src/cargo/ops/cargo_rustc/mod.rs
+++ b/src/cargo/ops/cargo_rustc/mod.rs
@@@ -11,8 -11,9 +11,9 @@@ use rustc_serialize::json
  use core::{Package, PackageId, PackageSet, Target, Resolve};
  use core::{Profile, Profiles, Workspace};
  use core::shell::ColorConfig;
 -use util::{self, CargoResult, ProcessBuilder, human, machine_message};
 +use util::{self, CargoResult, ProcessBuilder, ProcessError, human, machine_message};
  use util::{Config, internal, ChainError, profile, join_paths, short_hash};
+ use util::Freshness;
  
  use self::job::{Job, Work};
  use self::job_queue::JobQueue;

diff --cc tests/test.rs
Simple merge