Auto merge of #4149 - ordian:master, r=alexcrichton

Drop rustc-serialize dependency

Fixes #3944.

diff --cc Cargo.lock
index 781bfea05f67f30c74e121052755cbb2ca69e1a1,375d563857d05d0c1528f55e00f518f9eb709620..eb2efec09975e010e1feba363b8eced57811fe6f
--- 1/Cargo.lock
--- 2/Cargo.lock
+++ b/Cargo.lock
@@@ -24,10 -25,9 +25,9 @@@ dependencies = 
   "libgit2-sys 0.6.12 (registry+https://github.com/rust-lang/crates.io-index)",
   "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
   "miow 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
 - "num_cpus 1.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
 + "num_cpus 1.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
   "openssl 0.9.13 (registry+https://github.com/rust-lang/crates.io-index)",
   "psapi-sys 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
-  "rustc-serialize 0.3.24 (registry+https://github.com/rust-lang/crates.io-index)",
   "scoped-tls 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
   "semver 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
   "serde 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)",
@@@ -881,9 -874,9 +887,9 @@@ dependencies = 
  "checksum cmake 0.1.24 (registry+https://github.com/rust-lang/crates.io-index)" = "b8ebbb35d3dc9cd09497168f33de1acb79b265d350ab0ac34133b98f8509af1f"
  "checksum crossbeam 0.2.10 (registry+https://github.com/rust-lang/crates.io-index)" = "0c5ea215664ca264da8a9d9c3be80d2eaf30923c259d03e870388eb927508f97"
  "checksum curl 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)" = "c90e1240ef340dd4027ade439e5c7c2064dd9dc652682117bd50d1486a3add7b"
 -"checksum curl-sys 0.3.11 (registry+https://github.com/rust-lang/crates.io-index)" = "23e7e544dc5e1ba42c4a4a678bd47985e84b9c3f4d3404c29700622a029db9c3"
 +"checksum curl-sys 0.3.12 (registry+https://github.com/rust-lang/crates.io-index)" = "f00c8ba847fb0730c293069b4d1203dc01bf3c2e1f90b4e55f426ed8f4a1eeac"
  "checksum dbghelp-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "97590ba53bcb8ac28279161ca943a924d1fd4a8fb3fa63302591647c4fc5b850"
- "checksum docopt 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ab32ea6e284d87987066f21a9e809a73c14720571ef34516f0890b3d355ccfd8"
+ "checksum docopt 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "63e408eee8a772c5c61f62353992e3ebf51ef5c832dd04d986b3dc7d48c5b440"
  "checksum dtoa 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)" = "80c8b71fd71146990a9742fc06dcbbde19161a267e0ad4e572c35162f4578c90"
  "checksum env_logger 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)" = "3ddf21e73e016298f5cb37d6ef8e8da8e39f91f9ec8b0df44b7deb16a9f8cd5b"
  "checksum error-chain 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)" = "d9435d864e017c3c6afeac1654189b06cdb491cf2ff73dbf0d73b0f292f42ff8"

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