Patch #3: This patch does the following:
- Remove the HAVE_WVLA check since all used versions of GCC/Clang now supports -Wvla
- Remove HAVE_GETCURRENTPROCESSORNUMBER as it is true on all supported Windows versions
- Remove workaround for old Intellisense bug
- Unconditionally define S_IROTH/S_IFIFO on Windows rather than doing a check with hardcoded result
- Use SIGTERM/SIGINT explicitly on Windows rather than define SIGQUIT/SIGPIPE to them
- Use isnan() directly on Windows, remove unneeded check 
- Typedef ssize_t on Windows rather than doing check with hardcoded result 
- Remove HAVE_SCHED_H and HAVE_PTHREAD_YIELD_ZERO_ARG checks, results not needed anymore
- Remove HAVE_MMAP, always true
- Remove HAVE_SCHED_YIELD, always true on non-Windows 
- No point in testing size of char, defined to 1 in standard 
- Remove inline check, explicitly define for Visual Studio in C mode instead
- Combine separate C/C++ checks for builtin_unreachable as we now always use the same compiler for C/C++
- Remove HAVE_ACCESS, was never defined. Update code to work like intended.
- Set SOCKET_SIZE_TYPE, size_socket and sigset_t and mode_t using typedef rather than CMake #define 
- Remove unused FN_NO_CASE_SENCE, ulong_to_double() and table_case_convert().
- Remove use of non-standard pthread_yield(), use POSIX standard sched_yield() instead
- Remove unneeded thread pool config.h.cmake, add missing WindowsCache.cmake entry
- Rewrite InnoDB CMake futex check to avoid having to do unset/remove_definitions