Fix fprintf compilation error by including stdio in opus_compare wrapper

Author: yutotakano

test/opus_compare_wrapper.c

@@ -1,7 +1,17 @@
 // A wrapper for opus_compare.c which renames the main symbol to avoid conflits
 // with Haskell, and which disables the use of fprintf.
+
+// First, include stdio to prevent the fprintf definition later from breaking
+// the definition of fprintf
+#include <stdio.h>
+
+// Rewrite main to opus_compare_main to prevent conflits when FFI-ed
 #define main opus_compare_main
+
+// Rewrite all fprintf to a no-op
 #define fprintf(out,fmt,...)
 #include "opus_compare.c"
+
+// Undefine main and fprintf for safety
 #undef main
 #undef fprintf