wasapi: Fix build with Windows 8.1 SDK

With the Windows 8.1 SDK, the v1 of the AUDCLNT_STREAMOPTIONS enum is
defined which only has NONE and RAW, so it's not only defined when
AudioClient3 is available.

Add a meson check for the symbol. This is not needed for Autotools
because there we build against the MinGW audioclient.h which is still
at v1 of the AudioClient interface.
diff --git a/sys/wasapi/gstaudioclient3.h b/sys/wasapi/gstaudioclient3.h
index a9f240a..784f478 100644
--- a/sys/wasapi/gstaudioclient3.h
+++ b/sys/wasapi/gstaudioclient3.h
@@ -16,13 +16,14 @@
 #ifndef __IAudioClient3_INTERFACE_DEFINED__
 #define __IAudioClient3_INTERFACE_DEFINED__
 
-/* This is only available with IAudioClient3 */
+#ifndef HAVE_AUDCLNT_STREAMOPTIONS
 typedef enum AUDCLNT_STREAMOPTIONS
 {
     AUDCLNT_STREAMOPTIONS_NONE	        = 0,
     AUDCLNT_STREAMOPTIONS_RAW	        = 0x1,
     AUDCLNT_STREAMOPTIONS_MATCH_FORMAT	= 0x2
 } AUDCLNT_STREAMOPTIONS;
+#endif
 
 /* These should be available when the IAudioClient2 interface is defined */
 #ifndef __IAudioClient2_FWD_DEFINED__
diff --git a/sys/wasapi/meson.build b/sys/wasapi/meson.build
index f7bf995..a4cbc2d 100644
--- a/sys/wasapi/meson.build
+++ b/sys/wasapi/meson.build
@@ -10,9 +10,14 @@
   wasapi_dep = [cc.find_library('ole32'), cc.find_library('ksuser'),
                 cc.find_library('avrt', required : false)]
 
+  wasapi_args = ['-DCOBJMACROS']
+  if cc.has_header_symbol('audioclient.h', 'AUDCLNT_STREAMOPTIONS_NONE')
+    wasapi_args += ['-DHAVE_AUDCLNT_STREAMOPTIONS']
+  endif
+
   gstwasapi = library('gstwasapi',
     wasapi_sources,
-    c_args : gst_plugins_bad_args + ['-DCOBJMACROS'],
+    c_args : gst_plugins_bad_args + wasapi_args,
     include_directories : [configinc],
     dependencies : [gstaudio_dep] + wasapi_dep,
     install : true,