Fix -Wundef warnings due to use of unguarded SDL_AUDIO_DRIVER_WASAPI

src/audio/SDL_audio.c

@@ -46,7 +46,7 @@ static const AudioBootStrap *const bootstrap[] = {
 #ifdef SDL_AUDIO_DRIVER_NETBSD
     &NETBSDAUDIO_bootstrap,
 #endif
-#if SDL_AUDIO_DRIVER_WASAPI
+#ifdef SDL_AUDIO_DRIVER_WASAPI
     &WASAPI_bootstrap,
 #endif
 #if SDL_AUDIO_DRIVER_DSOUND

src/audio/wasapi/SDL_wasapi.c

@@ -20,7 +20,7 @@
 */
 #include "SDL_internal.h"
 
-#if SDL_AUDIO_DRIVER_WASAPI
+#ifdef SDL_AUDIO_DRIVER_WASAPI
 
 #include "../../core/windows/SDL_windows.h"
 #include "../../core/windows/SDL_immdevice.h"

src/audio/wasapi/SDL_wasapi_win32.c

@@ -26,7 +26,7 @@
    The code in SDL_wasapi.c is used by both standard Windows and WinRT builds
    to deal with audio and calls into these functions. */
 
-#if SDL_AUDIO_DRIVER_WASAPI && !defined(__WINRT__)
+#if defined(SDL_AUDIO_DRIVER_WASAPI) && !defined(__WINRT__)
 
 #include "../../core/windows/SDL_windows.h"
 #include "../../core/windows/SDL_immdevice.h"

src/audio/wasapi/SDL_wasapi_winrt.cpp

@@ -25,7 +25,7 @@
 //  is in SDL_wasapi_win32.c. The code in SDL_wasapi.c is used by both standard
 //  Windows and WinRT builds to deal with audio and calls into these functions.
 
-#if SDL_AUDIO_DRIVER_WASAPI && defined(__WINRT__)
+#if defined(SDL_AUDIO_DRIVER_WASAPI) && defined(__WINRT__)
 
 #include <Windows.h>
 #include <windows.ui.core.h>