Fix includes on Windows.

Author: ericsnowcurrently

Modules/posixmodule.c

@@ -14,6 +14,7 @@
 // is not exported by <windows.h> if the WIN32_LEAN_AND_MEAN macro is defined,
 // whereas pycore_condvar.h defines the WIN32_LEAN_AND_MEAN macro.
 #ifdef MS_WINDOWS
+#  include <winsock2.h>
 #  include <windows.h>
 #  include <pathcch.h>
 #  include <lmcons.h>             // UNLEN

PC/msvcrtmodule.c

@@ -23,6 +23,7 @@
 #include <conio.h>
 #include <sys/locking.h>
 #include <crtdbg.h>
+#include <winsock2.h>
 #include <windows.h>
 
 #ifdef _MSC_VER