Auto merge of #3719 - alexcrichton:curl-sys, r=alexcrichton

Update libz-sys

Try to fix AppVeyor CI

diff --cc Cargo.lock
index 761d6247d3eb503a51e275d67aa2968f9110ec16,c71b8893676e37e0de46b5b947a08fa112212d35..8617962f3f961a98eaa065b8e6ba7d605c52d5e8
--- 1/Cargo.lock
--- 2/Cargo.lock
+++ b/Cargo.lock
@@@ -761,9 -761,9 +761,9 @@@ dependencies = 
  "checksum kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "7507624b29483431c0ba2d82aece8ca6cdba9382bff4ddd0f7490560c056098d"
  "checksum lazy_static 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "6abe0ee2e758cd6bc8a2cd56726359007748fbf4128da998b65d0b70f881e19b"
  "checksum libc 0.2.20 (registry+https://github.com/rust-lang/crates.io-index)" = "684f330624d8c3784fb9558ca46c4ce488073a8d22450415c5eb4f4cfb0d11b5"
 -"checksum libgit2-sys 0.6.6 (registry+https://github.com/rust-lang/crates.io-index)" = "c7a4e33e9f8b8883c1a5898e72cdc63c00c4f2265283651533b00373094e901c"
 +"checksum libgit2-sys 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)" = "d951fd5eccae07c74e8c2c1075b05ea1e43be7f8952245af8c2840d1480b1d95"
  "checksum libssh2-sys 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)" = "91e135645c2e198a39552c8c7686bb5b83b1b99f64831c040a6c2798a1195934"
- "checksum libz-sys 1.0.12 (registry+https://github.com/rust-lang/crates.io-index)" = "7616099a575493da60cddc1174b686fcfb00ece89dc6f61f31ff47c35f07bbe8"
+ "checksum libz-sys 1.0.13 (registry+https://github.com/rust-lang/crates.io-index)" = "e5ee912a45d686d393d5ac87fac15ba0ba18daae14e8e7543c63ebf7fb7e970c"
  "checksum log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)" = "ab83497bf8bf4ed2a74259c1c802351fcd67a65baa86394b6ba73c36f4838054"
  "checksum matches 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "efd7622e3022e1a6eaa602c4cea8912254e5582c9c692e9167714182244801b1"
  "checksum memchr 0.1.11 (registry+https://github.com/rust-lang/crates.io-index)" = "d8b629fb514376c675b98c1421e80b151d3817ac42d7c667717d282761418d20"