Refactor: move processing functions to own header

src/common/processing.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#ifndef FF_INCLUDED_common_processing
+#define FF_INCLUDED_common_processing
+
+#include "util/FFstrbuf.h"
+
+void ffProcessAppendStdOut(FFstrbuf* buffer, char* const argv[]);
+
+#endif