CPPHTTPLIB_THREAD_POOL_COUNT allowed to be zero

[genakazachek]

If std::thread::hardware_concurrency() returns 1, which is possible for virtual environments, CPPHTTPLIB_THREAD_POOL_COUNT macro evaluate to zero leading to non working application

[yhirose]

@genakazachek, thank you for the feedback, but I probably don't fully understand the situation that you are talking about. In the current code, CPPHTTPLIB_THREAD_POOL_COUNT becomes at least 8 even when std::thread::hardware_concurrency() returns 1;

#define CPPHTTPLIB_THREAD_POOL_COUNT                                           \
  ((std::max)(8u, std::thread::hardware_concurrency() > 0                      \
                      ? std::thread::hardware_concurrency() - 1                \
                      : 0))

Hope it helps!