Updated SDL_syswm.h for SDL 3.0

* The header is no longer dependent on SDL build configuration
* The structures are versioned separately from the rest of SDL
* SDL_GetWindowWMInfo() now returns a standard result code and is passed the version expected by the application
* Updated WhatsNew.txt and docs/README-migration.md with the first API changes in SDL 3.0

test/testautomation_syswm.c

@@ -16,7 +16,7 @@
 int
 syswm_getWindowWMInfo(void *arg)
 {
-  SDL_bool result;
+  int result;
   SDL_Window *window;
   SDL_SysWMinfo info;
 
@@ -27,13 +27,10 @@ syswm_getWindowWMInfo(void *arg)
      return TEST_ABORTED;
   }
 
-  /* Initialize info structure with SDL version info */
-  SDL_VERSION(&info.version);
-
   /* Make call */
-  result = SDL_GetWindowWMInfo(window, &info);
+  result = SDL_GetWindowWMInfo(window, &info, SDL_SYSWM_CURRENT_VERSION);
   SDLTest_AssertPass("Call to SDL_GetWindowWMInfo()");
-  SDLTest_Log((result == SDL_TRUE) ? "Got window information" : "Couldn't get window information");
+  SDLTest_Log((result == 0) ? "Got window information" : "Couldn't get window information");
 
   SDL_DestroyWindow(window);
   SDLTest_AssertPass("Call to SDL_DestroyWindow()");

test/testnative.h

@@ -15,9 +15,6 @@
 */
 #include "SDL.h"
 
-/* This header includes all the necessary system headers for native windows */
-#include "SDL_syswm.h"
-
 typedef struct
 {
     const char *tag;
@@ -36,10 +33,6 @@ extern NativeWindowFactory X11WindowFactory;
 #endif
 
 #ifdef SDL_VIDEO_DRIVER_COCOA
-/* Actually, we don't really do this, since it involves adding Objective C
-   support to the build system, which is a little tricky.  You can uncomment
-   it manually though and link testnativecocoa.m into the test application.
-*/
 #define TEST_NATIVE_COCOA
 extern NativeWindowFactory CocoaWindowFactory;
 #endif

test/testnativew32.c

@@ -14,6 +14,8 @@
 
 #ifdef TEST_NATIVE_WINDOWS
 
+#include <windows.h>
+
 static void *CreateWindowNative(int w, int h);
 static void DestroyWindowNative(void *window);
 

test/testnativex11.c

@@ -14,6 +14,8 @@
 
 #ifdef TEST_NATIVE_X11
 
+#include <X11/Xlib.h>
+
 static void *CreateWindowX11(int w, int h);
 static void DestroyWindowX11(void *window);