bump autocfg to fix no_std probing

.travis.yml

@@ -14,6 +14,14 @@ script:
   - ./ci/test_full.sh
 matrix:
   include:
+    # try a target that doesn't have std at all
+    - name: "no_std"
+      rust: stable
+      env: TARGET=thumbv6m-none-eabi
+      before_script:
+        - rustup target add $TARGET
+      script:
+        - cargo build --verbose --target $TARGET --no-default-features --features i128
     - name: "rustfmt"
       rust: 1.31.0
       before_script:

Cargo.toml

@@ -24,4 +24,4 @@ std = []
 i128 = []
 
 [build-dependencies]
-autocfg = "0.1.2"
+autocfg = "0.1.3"