iomux_signal.h and wqueue.h should be usable in C++. Add

to IOMux doxygen group too.

include/ucore/iomux_signal.h

@@ -2,6 +2,15 @@
 #define UC_IOMUX_SIGNAL_H_
 
 #include "ucore/iomux.h"
+
+/** @addtogroup IOMux
+ *  @{ 
+ */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /** Callback signature for handling unix signals.
  * @param mux associated mux
  * @param signo unix signal number
@@ -45,4 +54,10 @@ int iomux_register_unixsignal(struct IOMux *mux,
  */
 int iomux_unregister_unixsignal(struct IOMux *mux, int signo);
 
+#ifdef __cplusplus
+}
+#endif
+
+/**  @} (addtogroup)*/
+
 #endif