turn audio.c and main.c into CPP files

fixes crash when trying to init audio on linux

test/audio.cpp

@@ -0,0 +1,77 @@
+#include "audio.h"
+
+#include <stdio.h>
+#include <pthread.h>
+#include <unistd.h>
+#include <sys/time.h>
+
+extern "C" {
+#include "../src/libsm64.h"
+#include "context.h"
+}
+
+static SDL_AudioDeviceID dev;
+
+pthread_t gSoundThread;
+long long timeInMilliseconds(void)
+{
+	struct timeval tv;
+	gettimeofday(&tv, NULL);
+
+	return(((long long)tv.tv_sec)*1000)+(tv.tv_usec/1000);
+}
+
+void* audio_thread(void* keepAlive)
+{
+	// from https://github.com/ckosmic/libsm64/blob/audio/src/libsm64.c#L535-L555
+	// except keepAlive is a null pointer here, so don't use it
+
+	pthread_setcancelstate(PTHREAD_CANCEL_ENABLE,NULL);
+	pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED,NULL);
+
+	long long currentTime = timeInMilliseconds();
+	long long targetTime = 0;
+	while(1)
+	{
+		//if(!*((bool*)keepAlive)) return NULL;
+
+		int16_t audioBuffer[544 * 2 * 2];
+		uint32_t numSamples = sm64_audio_tick(SDL_GetQueuedAudioSize(dev)/4, 1100, audioBuffer);
+		if (SDL_GetQueuedAudioSize(dev)/4 < 6000)
+			SDL_QueueAudio(dev, audioBuffer, numSamples * 2 * 4);
+
+		targetTime = currentTime + 33;
+		while (timeInMilliseconds() < targetTime)
+		{
+			usleep(100);
+			//if(!*((bool*)keepAlive)) return NULL;
+		}
+		currentTime = timeInMilliseconds();
+	}
+}
+
+void audio_init()
+{
+	if (SDL_InitSubSystem(SDL_INIT_AUDIO) < 0) {
+		fprintf(stderr, "SDL_InitSubSystem(SDL_INIT_AUDIO) failed: %s\n", SDL_GetError());
+		return;
+	}
+
+	SDL_AudioSpec want, have;
+	SDL_zero(want);
+	want.freq = 32000;
+	want.format = AUDIO_S16;
+	want.channels = 2;
+	want.samples = 512;
+	want.callback = NULL;
+	dev = SDL_OpenAudioDevice(NULL, 0, &want, &have, 0);
+	if (dev == 0) {
+		fprintf(stderr, "SDL_OpenAudio error: %s\n", SDL_GetError());
+		return;
+	}
+	SDL_PauseAudioDevice(dev, 0);
+
+	// it's best to run audio in a separate thread
+	pthread_create(&gSoundThread, NULL, audio_thread, NULL);
+}
+