add mpg123 test

test/libmpg123.cpp

@@ -0,0 +1,11 @@
+#include <mpg123.h>
+
+int main(int argc, char **argv)
+{
+	mpg123_init();
+	mpg123_handle* mh = mpg123_new(NULL, NULL);
+	mpg123_param(mh, MPG123_VERBOSE, 1, 0.);
+	mpg123_delete(mh);
+	mpg123_exit();
+	return 0;
+}