Improve doxygen documentation.

include/ucore/iomux_waker.h

@@ -15,16 +15,19 @@ struct IOMuxSignaller {
     int fd;
 };
 
-/** These are primitives to wake up an IOMux.
+/** @file
+ * These are primitives to wake up an IOMux.
  * An IOMux event loop can be woken up from e.g. an unix signal handler
  * or another thread. The IOMuxWaker itself is not thread safe, it's members
- * must not be accessed from anything other than the loop it's connected to.
+ * except for the signaller must not be accessed from anything other than the 
+ * IOMux it's connected to.
  * Only uc_iomux_waker_signal() can be called from another thread/signal handler
  * than the IOMux it's connected to.
  * 
  * Note that several signals to wake up a loop can get merged, the callback
  * handler can be called only once for several signals.
  */
+
 struct IOMuxWaker {
     //private fields
     struct IOMuxFD read_fd;