wasapi: Initial WASAPI support, for Windows Vista and later.

This should remain binary compatible with Windows XP, as we dynamically
load anything we need and fall back to DirectSound/WinMM/XAudio2 if not
available.

VisualC/SDL/SDL.vcxproj

@@ -361,6 +361,7 @@
     <ClInclude Include="..\..\src\video\windows\SDL_windowsshape.h" />
     <ClInclude Include="..\..\src\video\windows\SDL_windowsvideo.h" />
     <ClInclude Include="..\..\src\video\windows\SDL_windowswindow.h" />
+    <ClInclude Include="..\..\src\audio\wasapi\SDL_wasapi.h" />
     <ClInclude Include="..\..\src\audio\winmm\SDL_winmm.h" />
     <ClInclude Include="..\..\src\core\windows\SDL_xinput.h" />
     <ClInclude Include="..\..\src\haptic\windows\SDL_xinputhaptic_c.h" />
@@ -491,6 +492,7 @@
     <ClCompile Include="..\..\src\video\windows\SDL_windowsshape.c" />
     <ClCompile Include="..\..\src\video\windows\SDL_windowsvideo.c" />
     <ClCompile Include="..\..\src\video\windows\SDL_windowswindow.c" />
+    <ClCompile Include="..\..\src\audio\wasapi\SDL_wasapi.c" />
     <ClCompile Include="..\..\src\audio\winmm\SDL_winmm.c" />
     <ClCompile Include="..\..\src\audio\xaudio2\SDL_xaudio2.c" />
     <ClCompile Include="..\..\src\core\windows\SDL_xinput.c" />

VisualC/SDL/SDL_VS2008.vcproj

@@ -1437,6 +1437,14 @@
 			RelativePath="..\..\src\video\windows\SDL_windowswindow.h"
 			>
 		</File>
+		<File
+			RelativePath="..\..\src\audio\wasapi\SDL_wasapi.c"
+			>
+		</File>
+		<File
+			RelativePath="..\..\src\audio\wasapi\SDL_wasapi.h"
+			>
+		</File>
 		<File
 			RelativePath="..\..\src\audio\winmm\SDL_winmm.c"
 			>

include/SDL_config_windows.h

@@ -154,6 +154,7 @@ typedef unsigned int uintptr_t;
 #endif
 
 /* Enable various audio drivers */
+#define SDL_AUDIO_DRIVER_WASAPI 1
 #define SDL_AUDIO_DRIVER_DSOUND 1
 #define SDL_AUDIO_DRIVER_XAUDIO2    1
 #define SDL_AUDIO_DRIVER_WINMM  1

src/audio/SDL_audio.c

@@ -68,6 +68,9 @@ static const AudioBootStrap *const bootstrap[] = {
 #if SDL_AUDIO_DRIVER_NAS
     &NAS_bootstrap,
 #endif
+#if SDL_AUDIO_DRIVER_WASAPI
+    &WASAPI_bootstrap,
+#endif
 #if SDL_AUDIO_DRIVER_XAUDIO2
     &XAUDIO2_bootstrap,
 #endif