Fix MSVC linter warning about uninitialized TestSuite variables

[Reedbeta]

In MSVC 2019 the Intellisense linter pops a warning whenever I used TEST_SUITE. It was unhappy that the static doctest::detail::TestSuite data was uninitialized. Fixed by default-initializing that in two places where it appears. Thanks!

[Reedbeta]

OK, the CI is failing and I am not sure why this is not working when compiled as C++11... the TestSuite struct is all trivial types, so it should just be getting zero-filled??

[Reedbeta]

I think the CI is just running this on some really old and buggy versions of gcc. 😕

[onqtam]

I guess we should be able to get the old GCC builds running by silencing -Wmissing-field-initializers around the problematic pieces of code like this:

DOCTEST_GCC_SUPPRESS_WARNING_WITH_PUSH("-Wmissing-field-initializers")
// ... code with ={};
DOCTEST_GCC_SUPPRESS_WARNING_POP

[Reedbeta]

Alright, I put the warning suppress in, but it's still failing gcc 4.8 and 4.9. 🤪 Doesn't make any sense. I even tried it on godbolt to verify that warning can be suppressed, and it works fine there.

[onqtam]

Let's merge this and I'll try to figure out how to get gcc 4.8 & 4.9 not to complain. Thanks!