The most likely cause of the crash is that a timer fired, after it was closed.

MSDN documents such a possibility, in the documentation for
CloseThreadpoolTimer() function, and recommends disabling the timer before
calling WaitForThreadpoolTimerCallbacks()/CloseThreadpoolTimer().

The fix follows this recommendation.

Note, that 5.5-10.1 disabled the timer before close, but this code
was lost in threadpool refactoring in 10.2

- Do not scan registry to check if TCPIP is supported.
- Do not read registry under HKEY_LOCAL_MACHINE\SOFTWARE\MySQL anymore.
- Do not load threadpool function dynamically, it is available
since Win7.
- simplify win32_init_tcp_ip(), and return error of WSAStartup() fails.
- Correct comment in my_parameter_handler()