travis: add a CMake build

Uses an out-of-tree build; in-tree builds do not work.

No make uninstall test (CMake does not support this).

.travis.yml

@@ -25,6 +25,24 @@ matrix:
             - g++-multilib
       env:
           - CXXFLAGS="-g -O2 -m32" CFLAGS="-g -m32"
+    - os: linux
+      compiler: clang
+      addons:
+        apt:
+          packages:
+            - bc
+            - expect
+            - gettext
+            - libncurses5-dev
+            - cmake
+      env:
+        - USE_CMAKE="1" # Dummy value, shows up in the Travis UI only
+      script:
+        - mkdir build && cd build &&
+          cmake -DCMAKE_INSTALL_PREFIX=$HOME/prefix .. || cat CMakeFiles/CMakeError.log &&
+          make -j2 &&
+          make install &&
+          make test SHOW_INTERACTIVE_LOG=1
     - os: linux
       compiler: clang
       env: