Run ThemisPP tests with C++14 and C++17 (#572)

Explicitly test compatibility with those standard levels. C++20 is
currently being finalized. It's somewhat supported in the compilers,
but not in the versions shipped with Ubuntu 16.04.

It turned out that behavior wrt attributes might be different between
GCC and Clang, so let's test both compilers now.

Clang that we have in the Docker image does not support "-std=c++17",
so we do not test with that. (Actually, GCC support the option, but
__cplusplus value suggests that it's still in C++14 mode.)

.circleci/config.yml

@@ -155,8 +155,15 @@ jobs:
       - run: '[ -z "$CIRCLE_PR_NUMBER" ] && ! [ -z "$COVERALLS_TOKEN" ] && cd $HOME/go/src/$GOTHEMIS_IMPORT && $HOME/go/bin/goveralls -v -service=circle-ci -repotoken=$COVERALLS_TOKEN || true'
       - run: sudo /sbin/ldconfig
       - run: make test
-      - run: make clean_themispp_test && CFLAGS="-std=c++03" make themispp_test && make test_cpp
-      - run: make clean_themispp_test && CFLAGS="-std=c++11" make themispp_test && make test_cpp
+      - run: make clean_themispp_test && CXX="g++"     CFLAGS="-std=c++03" make themispp_test && make test_cpp
+      - run: make clean_themispp_test && CXX="g++"     CFLAGS="-std=c++11" make themispp_test && make test_cpp
+      - run: make clean_themispp_test && CXX="g++"     CFLAGS="-std=c++14" make themispp_test && make test_cpp
+      - run: make clean_themispp_test && CXX="g++"     CFLAGS="-std=c++17" make themispp_test && make test_cpp
+      - run: make clean_themispp_test && CXX="clang++" CFLAGS="-std=c++03" make themispp_test && make test_cpp
+      - run: make clean_themispp_test && CXX="clang++" CFLAGS="-std=c++11" make themispp_test && make test_cpp
+      - run: make clean_themispp_test && CXX="clang++" CFLAGS="-std=c++14" make themispp_test && make test_cpp
+      # Clang 3.8 that we have here does not support C++17 yet
+#     - run: make clean_themispp_test && CXX="clang++" CFLAGS="-std=c++17" make themispp_test && make test_cpp
       - run: make test_python
       - run: make test_ruby
       - run: make test_go

CHANGELOG.md

@@ -18,6 +18,7 @@ _Code:_
 - **C++**
 
   - New function `themispp::gen_sym_key()` can be used to generate symmetric keys for Secure Cell ([#561](https://github.com/cossacklabs/themis/pull/561)).
+  - Updated test suite to test C++14 and C++17 (in addition to C++11 and C++03) ([#572](https://github.com/cossacklabs/themis/pull/572)).
 
 - **Go**