Add windows_with_undefs.h to fix conflicts with windows.h

windows.h adds macros such as `#define GetMessage GetMessageA` which
cause conflicts in naming when for example a class definition is before
windows.h and a use is after windows.h

Add a header that can be used both to include windows.h and remove
defines, and to only remove defines (when windows.h is included by)
external dependencies.

src/backend/d3d12/d3d12_platform.h

@@ -25,4 +25,10 @@
 
 using Microsoft::WRL::ComPtr;
 
+// Remove windows.h macros after d3d12's include of windows.h
+#include "common/Platform.h"
+#if defined(NXT_PLATFORM_WINDOWS)
+#    include "common/windows_with_undefs.h"
+#endif
+
 #endif  // BACKEND_D3D12_D3D12PLATFORM_H_

src/backend/opengl/DeviceGL.h

@@ -19,9 +19,15 @@
 
 #include "backend/Device.h"
 #include "backend/opengl/Forward.h"
+#include "common/Platform.h"
 
 #include "glad/glad.h"
 
+// Remove windows.h macros after glad's include of windows.h
+#if defined(NXT_PLATFORM_WINDOWS)
+#    include "common/windows_with_undefs.h"
+#endif
+
 namespace backend { namespace opengl {
 
     class Device : public DeviceBase {

src/common/CMakeLists.txt

@@ -30,6 +30,7 @@ list(APPEND COMMON_SOURCES
     ${COMMON_DIR}/SerialQueue.h
     ${COMMON_DIR}/SwapChainUtils.h
     ${COMMON_DIR}/vulkan_platform.h
+    ${COMMON_DIR}/windows_with_undefs.h
 )
 
 add_library(nxt_common STATIC ${COMMON_SOURCES})

src/common/DynamicLib.cpp

@@ -17,7 +17,7 @@
 #include "common/Platform.h"
 
 #if NXT_PLATFORM_WINDOWS
-#    include <windows.h>
+#    include "common/windows_with_undefs.h"
 #elif NXT_PLATFORM_POSIX
 #    include <dlfcn.h>
 #else

src/common/vulkan_platform.h

@@ -87,4 +87,10 @@ class VkNonDispatchableHandle {
 #    undef VK_NULL_HANDLE
 #    define VK_NULL_HANDLE nullptr
 
+// Remove windows.h macros after vulkan_platform's include of windows.h
+#include "common/Platform.h"
+#if defined(NXT_PLATFORM_WINDOWS)
+#    include "common/windows_with_undefs.h"
+#endif
+
 #endif  // COMMON_VULKANPLATFORM_H_

src/common/windows_with_undefs.h

@@ -0,0 +1,31 @@
+// Copyright 2018 The NXT Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef COMMON_WINDOWS_WITH_UNDEFS_H_
+#define COMMON_WINDOWS_WITH_UNDEFS_H_
+
+#include "common/Compiler.h"
+
+#if !defined(NXT_PLATFORM_WINDOWS)
+#    error "windows_with_undefs.h included on non-Windows"
+#endif
+
+// This header includes <windows.h> but removes all the extra defines that conflict with identifiers
+// in internal code. It should never be included in something that is part of the public interface.
+#include <windows.h>
+
+// Macros defined for ANSI / Unicode support
+#undef GetMessage
+
+#endif  // COMMON_WINDOWS_WITH_UNDEFS_H_