We need this to merge the game specific sector/wall extensions with the base but still allow the engine to access such arrays. For that they need a runtime settable stride.
Since everything uses the same warning number, the old setup resulted in [[deprecated]] being silenced.
So this explicitly adds the needed #defines to silence the very noisy warning from the MSVC headers but leaves warning 4996 active otherwise.
In particlular this does:
* silence all warnings in the subprojects
* do not derive TIterator from std::iterator anymore as C++17 deprecates this.
* silence the above for RapidJSON because altering that code is not desirable.
* explicitly disable warning 4996 in some Windows files that call the deprecated (but still needed) GetVersionEx function.
* define _CRT_SECURE_NO_DEPRECATE, _CRT_SECURE_NO_WARNINGS and _CRT_NONSTDC_NO_WARNINGS through CMake to disable the CRT's deprecation and security warnings.
Currently this will print several (intended) deprecation warnings about 'updatesector' that point to code that needs to be changed but cannot yet without other refactorings being done first.
Fixes:
* do not strip 'filter' as a directory prefix.
* proper spacing for scaled sheet fonts.
* fix of transparent color in BMF fonts.
* fix restart button on error pane in Windows.
* do not skip over empty 'if's with a condition that would error out.
Although the images themselves are automatically taken down, any memory they allocate is not - and some of the special tile classes do need dynamic storage.
* Serves no purpose in Raze or GZDoom and appears to only have been added to the backend to facilitate the older interpolation code that was excised in 893686709b.
