The use we previously used the polyfill or naked new is that we
supported C++11, which did not yet have `std::make_unique`. However,
with the move to C++14 as the minimum, `std::make_unique` can be
expected to be always available.
This should decrease the number of allocations before main is entered
significantly, but complicates the code somewhat in return.
Assuming I used `massif` right, doing just `SelfTest --list-tests`
went from 929 allocations at "Remove gcc-4.9 from the travis builds"
(2 commits up), to 614 allocations with this commit.
Now a `TEST_CASE` macro should create a single TestCaseInfo and then
it should never be copied around. This, together with latter changes,
should significantly decrease the number of allocations made before
`main` is even entered.
* Use Xenial as the base distribution
* Remove C++11 builds
* Add a lot more C++14 builds
* Add some C++17 builds
* Include newer versions of Clang and GCC
Prevent warnings
- gnu: -Wcomment: multi-line comment
- clang: -Wweak-vtables 'class' has no out-of-line virtual method definitions; its vtable will be emitted in every translation unit
- clang: -Winconsistent-missing-override: 'method' overrides a member function but is not marked 'override'
- MSVC: C4702: unreachable code
This also goes for pkg-config installed by our CMake installation.
This includes
* Updating CMake version on Travis
* Adding a `Catch2` subfolder to the `single_include/` folder to
provide this include path both _inside_ the repository, and _outside_.
* Updated examples to build with the new paths
* Other general CMake cleanup
