Added Android audio backend

This *should* add the Android audio backend. I do not have any idea how
to do this properly, but I figured that this might work for the moment.
There's probably a lot of testing required for this to work.

core/oslib/audiobackend_android.h

@@ -0,0 +1,4 @@
+#pragma once
+#include "oslib/audiostream.h"
+
+extern audiobackend_t audiobackend_android;

core/oslib/audiostream.cpp

@@ -3,6 +3,7 @@
 #include "oslib/oslib.h"
 #include "audiostream.h"
 #include "oslib/audiobackend_directsound.h"
+#include "oslib/audiobackend_android.h"
 #include "oslib/audiobackend_alsa.h"
 #include "oslib/audiobackend_oss.h"
 
@@ -73,6 +74,9 @@ void RegisterAllAudioBackends() {
 		#if HOST_OS==OS_WINDOWS
 		RegisterAudioBackend(&audiobackend_directsound);
 		#endif
+		#if ANDROID
+		RegisterAudioBackend(&audiobackend_android);
+		#endif
 		#if USE_OSS
 		RegisterAudioBackend(&audiobackend_oss);
 		#endif

shell/android/jni/src/Android.cpp

@@ -16,6 +16,7 @@
 #include "rend/TexCache.h"
 #include "hw/maple/maple_devs.h"
 #include "hw/maple/maple_if.h"
+#include "oslib/audiobackend_android.h"
 
 #include "util.h"
 
@@ -485,21 +486,38 @@ JNIEXPORT void JNICALL Java_com_reicast_emulator_emu_JNIdc_initControllers(JNIEn
 	env->ReleaseBooleanArrayElements(controllers, controllers_body, 0);
 }
 
-#if 0
-u32 PushAudio(void* frame, u32 amt, bool wait)
+// Audio Stuff
+u32 androidaudio_push(void* frame, u32 amt, bool wait)
 {
 	verify(amt==SAMPLE_COUNT);
 	//yeah, do some audio piping magic here !
 	jenv->SetShortArrayRegion(jsamples,0,amt*2,(jshort*)frame);
 	return jenv->CallIntMethod(emu,writemid,jsamples,wait);
 }
-#endif
+
+void androidaudio_init()
+{
+  // Nothing to do here...
+}
+
+void androidaudio_term()
+{
+  // Move along, there is nothing to see here!
+}
 
 bool os_IsAudioBuffered()
 {
     return jenv->CallIntMethod(emu,writemid,jsamples,-1)==0;
 }
 
+audiobackend_t audiobackend_android = {
+    "android", // Slug
+    "Android Audio", // Name
+    &androidaudio_init,
+    &androidaudio_push,
+    &androidaudio_term
+};
+
 int get_mic_data(u8* buffer)
 {
 	jbyteArray jdata = (jbyteArray)jenv->CallObjectMethod(sipemu,getmicdata);