audio_core: Add '#include <cstring>' to cubeb_sink and cubeb_input.cpp (#2232)

* audio_core: Add '#include <cstring>' to cubeb_sink and cubeb_input.cpp

This fixes a build failure encountered when compiling: https://pastebin.com/JQ4mbhyu

* Fix: License header

src/audio_core/cubeb_input.cpp

@@ -2,6 +2,7 @@
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
+#include <cstring>
 #include <utility>
 #include <vector>
 #include <cubeb/cubeb.h>

src/audio_core/cubeb_sink.cpp

@@ -1,8 +1,9 @@
-// Copyright 2018 Citra Emulator Project
+// Copyright Citra Emulator Project / Azahar Emulator Project
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
 #include <cstdarg>
+#include <cstring>
 #include <mutex>
 #include <vector>
 #include <cubeb/cubeb.h>