Auto merge of #1830 - alexcrichton:cap-lints, r=brson

This commit adds support to Cargo to pass `--cap-lints allow` to all upstream
dependencies instead of `-A warings`. This should serve the same purpose of
suppressing warnings in upstream dependencies as well as preventing widespread
breakage whenever a change to a lint is introduced in the compiler.

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 78cffdc044d91a69989e702827024603d50d1741,aac936656a5b2e2b0ec596c004704eb6d9b53dc7..25d9f2a02fe99b1f92cae49ce6adacfe3c7653b4
--- 1/src/cargo/ops/cargo_rustc/mod.rs
--- 2/src/cargo/ops/cargo_rustc/mod.rs
+++ b/src/cargo/ops/cargo_rustc/mod.rs
@@@ -1,9 -1,9 +1,9 @@@
  use std::collections::{HashSet, HashMap};
  use std::env;
 -use std::ffi::OsString;
 +use std::ffi::{OsStr, OsString};
  use std::fs;
  use std::io::prelude::*;
- use std::path::{self, Path, PathBuf};
+ use std::path::{self, PathBuf};
  use std::sync::Arc;
  
  use core::{SourceMap, Package, PackageId, PackageSet, Target, Resolve};

diff --cc src/cargo/util/config.rs
Simple merge

diff --cc tests/tests.rs
Simple merge