avplay: Accept cpuflags option

Quite useful for debugging.

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

cmdutils.h

@@ -71,6 +71,11 @@ void uninit_opts(void);
  */
 void log_callback_help(void* ptr, int level, const char* fmt, va_list vl);
 
+/**
+ * Override the cpuflags mask.
+ */
+int opt_cpuflags(void *optctx, const char *opt, const char *arg);
+
 /**
  * Fallback for options that are not explicitly handled, these will be
  * parsed through AVOptions.