Introduce Travis CI tests

In order to libbpf to be used in systemd some testing is required, see related
discussions in https://github.com/systemd/systemd/pull/12151 and
https://github.com/libbpf/libbpf/pull/29
The tests introduced here mirrors the tests of systemd:
For Debian: build with gcc, gcc + asan, clang, clang + asan
Debian tests use `docker` virtualization
Fror Ubuntu Xenial: build with gcc

The differences:
Install only libelf and it's dependencies.
Instead of Meson build system `make` is used, so `make` remains the preferred
method of building and `meson.build` doesn't get rooted in `libbpf`.

`travis_wait.bash` is kept as a workaround for
https://github.com/travis-ci/travis-ci/issues/9979

An example of testing UI: https://travis-ci.org/wat-ze-hex/libbpf

.travis.yml

@@ -0,0 +1,91 @@
+sudo: required
+dist: xenial
+services:
+    - docker
+
+env:
+    global:
+        - AUTHOR_EMAIL="$(git log -1 $TRAVIS_COMMIT --pretty=\"%aE\")"
+        - CI_MANAGERS="$TRAVIS_BUILD_DIR/travis-ci/managers"
+        - REPO_ROOT="$TRAVIS_BUILD_DIR"
+
+jobs:
+    include:
+        - stage: Build & test
+          name: Debian Testing
+          language: bash
+          env:
+              - DEBIAN_RELEASE="testing"
+              - CONT_NAME="libbpf-debian-$DEBIAN_RELEASE"
+              - DOCKER_EXEC="docker exec -ti $CONT_NAME"
+          before_install:
+              - sudo apt-get -y -o Dpkg::Options::="--force-confnew" install docker-ce
+              - docker --version
+          install:
+              - $CI_MANAGERS/debian.sh SETUP
+          script:
+              - set -e
+              - $CI_MANAGERS/debian.sh RUN
+              - set +e
+          after_script:
+              - $CI_MANAGERS/debian.sh CLEANUP
+
+        - name: Debian Testing (ASan+UBSan)
+          language: bash
+          env:
+              - DEBIAN_RELEASE="testing"
+              - CONT_NAME="libbpf-debian-$DEBIAN_RELEASE"
+              - DOCKER_EXEC="docker exec -ti $CONT_NAME"
+          before_install:
+              - sudo apt-get -y -o Dpkg::Options::="--force-confnew" install docker-ce
+              - docker --version
+          install:
+              - $CI_MANAGERS/debian.sh SETUP
+          script:
+              - set -e
+              - $CI_MANAGERS/debian.sh RUN_ASAN
+              - set +e
+          after_script:
+              - $CI_MANAGERS/debian.sh CLEANUP
+
+        - name: Debian Testing (clang)
+          language: bash
+          env:
+              - DEBIAN_RELEASE="testing"
+              - CONT_NAME="libbpf-debian-$DEBIAN_RELEASE"
+              - DOCKER_EXEC="docker exec -ti $CONT_NAME"
+          before_install:
+              - sudo apt-get -y -o Dpkg::Options::="--force-confnew" install docker-ce
+              - docker --version
+          install:
+              - $CI_MANAGERS/debian.sh SETUP
+          script:
+              - set -e
+              - $CI_MANAGERS/debian.sh RUN_CLANG
+              - set +e
+          after_script:
+              - $CI_MANAGERS/debian.sh CLEANUP
+
+        - name: Debian Testing (clang ASan+UBSan)
+          language: bash
+          env:
+              - DEBIAN_RELEASE="testing"
+              - CONT_NAME="libbpf-debian-$DEBIAN_RELEASE"
+              - DOCKER_EXEC="docker exec -ti $CONT_NAME"
+          before_install:
+              - sudo apt-get -y -o Dpkg::Options::="--force-confnew" install docker-ce
+              - docker --version
+          install:
+              - $CI_MANAGERS/debian.sh SETUP
+          script:
+              - set -e
+              - $CI_MANAGERS/debian.sh RUN_CLANG_ASAN
+              - set +e
+          after_script:
+              - $CI_MANAGERS/debian.sh CLEANUP
+        - name: Ubuntu Xenial
+          language: bash
+          script:
+              - set -e
+              - sudo $CI_MANAGERS/xenial.sh
+              - set +e