Rename SDL2 backend source files.

extras/backends/sdl2/miniaudio_sdl2.h

@@ -0,0 +1,34 @@
+/*
+The SDL2 backend does not require any user data, nor configs. Configs are provided here in case
+they are needed in the future, however you can safely pass in NULL when setting up your context
+and device configs.
+*/
+#ifndef miniaudio_backend_sdl2_h
+#define miniaudio_backend_sdl2_h
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern ma_device_backend_vtable* ma_device_backend_sdl2;
+
+
+typedef struct
+{
+    int _unused;
+} ma_context_config_sdl2;
+
+MA_API ma_context_config_sdl2 ma_context_config_sdl2_init(void);
+
+
+typedef struct
+{
+    int _unused;
+} ma_device_config_sdl2;
+
+MA_API ma_device_config_sdl2 ma_device_config_sdl2_init(void);
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* miniaudio_backend_sdl_h */