src/MemoryPool.cpp: Work around missing std::align on GCC 4.x

[mkoeppe]

This allows primesieve to build on some old distributions still supported by SageMath, including linuxmint-17 (https://github.com/mkoeppe/primesieve/runs/4342272538?check_suite_focus=true) and ubuntu-trusty.

[kimwalisch]

Hi Matthias,

I am sorry but I have to reject your pull request. As per primesieve's documentation the minimum requirements for primesieve-7.* are: a compiler that supports C++11 (or later) and CMake ≥ 3.4. If you need to build primesieve on old OSes and/or compilers you can try primesieve-6.4, it might work, but I don't provide any support for that use case.

As a general rule of thumb, I value contributions that benefit all of primesieve's users. But I do not accept workarounds or features that benefit a single project (in this case SageMath) or user.

[mkoeppe]

Thanks for the quick reaction. In this case you may want to edit the GH Actions workflow, removing the configurations that you do not intend to support.

[mkoeppe]

Just for reference, we carry this as a patch in https://trac.sagemath.org/ticket/25009#comment:78