Fix read violation crash in psutil.cpu_count(logical=False)

[samertm]

• Fix read violation crash in psutil.cpu_count(logical=False) by stopping the iteration through the SYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX buffer when we hit the last item.

The previous code would read one item off the end because offset equals length for the last element, but the code only checks that offset + ptr->Size <= length at the top of the iteration, which means it would always dereference ptr->Size where ptr points to memory that wasn't allocated to buffer. That occasionally causes read violation crashes.

• Remove the ptr->Size > 0 check because the struct size should never be 0 or something terribly wrong has happened.

To repro the crash, I did the following in cmd.exe:

# Enable full page heap verification on python.exe with gflags
> "C:\Program Files (x86)\Windows Kits\10\Debuggers\x64\gflags" /p /enable python.exe /full
> C:\Python37\python.exe
>>> import psutils
>>> psutil.cpu_count(logical=False)
# python.exe crashes and returns to the shell prompt
# IMPORTANT! When done testing, make sure to disable full page heap verification
>  "C:\Program Files (x86)\Windows Kits\10\Debuggers\x64\gflags" /p /disable python.exe