Include windows.h in conn_pty.h too to ensure it's right.

src/syncterm/conn_conpty.h

 #ifndef CONN_CONPTY_H
 #define CONN_CONPTY_H
 #ifdef _WIN32
+
+// We need to #include windows.h for NTDDI_VERSION to be rightified.
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+
 #if NTDDI_VERSION >= 0x0A000006
 
 #define HAS_CONPTY