travis: add scan-build

Closes #3564

.travis.yml

@@ -146,6 +146,10 @@ matrix:
           compiler: clang
           dist: trusty
           env: T=tidy
+        - os: linux
+          compiler: clang
+          dist: trusty
+          env: T=scan-build
         - os: linux
           compiler: clang
           dist: trusty
@@ -404,6 +408,11 @@ script:
           ./mainline.sh ${CURLSRC}
           popd
         fi
+    - |
+        if [ "$T" = "scan-build" ]; then
+             scan-build ./configure --enable-debug --enable-werror $C
+             scan-build --status-bugs make && scan-build --status-bugs make examples
+        fi
 
 # whitelist branches to avoid testing feature branches twice (as branch and as pull request)
 branches: