Fix gcc builds failing on windows

platform/windows/display_server_windows.cpp

@@ -2409,8 +2409,8 @@ void DisplayServerWindows::set_icon(const Ref<Image> &p_icon) {
 		SendMessage(windows[MAIN_WINDOW_ID].hWnd, WM_SETICON, ICON_BIG, (LPARAM)hicon);
 	} else {
 		icon = Ref<Image>();
-		SendMessage(windows[MAIN_WINDOW_ID].hWnd, WM_SETICON, ICON_SMALL, NULL);
-		SendMessage(windows[MAIN_WINDOW_ID].hWnd, WM_SETICON, ICON_BIG, NULL);
+		SendMessage(windows[MAIN_WINDOW_ID].hWnd, WM_SETICON, ICON_SMALL, 0);
+		SendMessage(windows[MAIN_WINDOW_ID].hWnd, WM_SETICON, ICON_BIG, 0);
 	}
 }
 

platform/windows/gl_manager_windows.cpp

@@ -53,6 +53,7 @@
 #if defined(__GNUC__)
 // Workaround GCC warning from -Wcast-function-type.
 #define wglGetProcAddress (void *)wglGetProcAddress
+#define GetProcAddress (void *)GetProcAddress
 #endif
 
 typedef HGLRC(APIENTRY *PFNWGLCREATECONTEXTATTRIBSARBPROC)(HDC, HGLRC, const int *);