Verify that only non-technical breaking changes are applied to libc

Closes #270 .

.travis.yml

@@ -11,6 +11,13 @@ stages:
 matrix:
   include:
     # TOOLS
+    - name: "Semver"
+      env: TARGET=x86_64-unknown-linux-gnu
+      install: |
+        travis_retry cargo +nightly install \
+        --git https://github.com/gnzlbg/rust-semverver \
+        --branch fix_exit_code
+      script: cargo +nightly semver --api-guidelines --target="${TARGET}"
     - name: "Documentation"
       env: TARGET=x86_64-unknown-linux-gnu
       script: sh ci/dox.sh