Imrpove CI

[FranckRJ]

• Test more versions of current compilers
• Test with more standards of C++
• Test with sanitizers enabled
• Test on Apple Clang
• Test on MinGW
• Move the MSVC tests in GitHub actions
• Run MSVC tests, currently it's only built but not run
• Run MSVC tests in 64 bits
• Run RTTI-dependent tests in MSVC 64 bits.
• Run C++14 specific tests for MSVC

Take inspiration from range-v3 CI configuration, which looks great : https://github.com/ericniebler/range-v3/blob/master/.github/workflows/range-v3-ci.yml

[malcolmdavey]

That would be good. Just tried to get it to compile with VS 2019/v142 with the existing appveyor, but seems to need more steps to enable toolsets/compiler versions.
Also would need to get the tests running for MSVC/VS

Edit - looks like I do have it working for VS 2015(v140) with C++14, and VS 2019 (v142) with C++20 and __cplusplus correct.
But it would be better with github actions etc.

[FranckRJ]

#313 improved things but there's still some things to fix to properly be able to test MSVC.

I'll probably remove the line "add more compilers" because I don't really want to invest a lot of time into supporting them.

[FranckRJ]

#317 fixed C++14 tests on MSVC. The only known issue remaining is with RTTI stuff on MSVC x64.

[FranckRJ]

With #318 now there's an action to run tests with sanitizers enabled.

[ClausKlein]

With #319 CI test with AppleClang on OSX may be added.

[FranckRJ]

With #335 now tests are run for MSVC 64 bits (expect tests that depend on RTTI as it isn't properly supported in fakeit for this configuration yet).