code review 4926042: runtime: use cgo runtime functions to call windows syscalls

src/pkg/runtime/windows/os.h

 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 extern void *runtime·LoadLibraryEx;
 extern void *runtime·GetProcAddress;
 
 // Call a Windows function with stdcall conventions,
 // and switch to os stack during the call.
 #pragma varargck        countpos        runtime·stdcall 2
 #pragma varargck        type            runtime·stdcall void*
 #pragma varargck        type            runtime·stdcall uintptr
-void runtime·asmstdcall(WinCall *c);
+void runtime·asmstdcall(void *c);
 void *runtime·stdcall(void *fn, int32 count, ...);
 uintptr runtime·syscall(void *fn, uintptr nargs, void *args, uintptr *err);
 
 uintptr runtime·getlasterror(void);
 void runtime·setlasterror(uintptr err);
 
 // Function to be called by windows CreateThread
 // to start new os thread.
 uint32 runtime·tstart_stdcall(M *newm);
 
 uint32 runtime·issigpanic(uint32);
 void runtime·sigpanic(void);
 uint32 runtime·ctrlhandler(uint32 type);
 
 // Windows dll function to go callback entry.
 byte *runtime·compilecallback(Eface fn, bool cleanstack);
 void *runtime·callbackasm(void);