docs: silence warnings about generated API docs

I noticed these while testing 'make dist'.

Parsing ./../src/util/event.c
Function comment for virEventRegisterDefaultImpl lacks description of return value
Function comment for virEventRunDefaultImpl lacks description of return value
Parsing ./../src/util/virterror.c
Missing comment for function virSetErrorLogPriorityFunc

* src/util/event.c (virEventRegisterDefaultImpl)
(virEventRunDefaultImpl): Document return types.
* src/util/virterror.c (virSetErrorLogPriorityFunc): Provide docs.

src/util/event.c

@@ -1,8 +1,8 @@
 /*
  * event.c: event loop for monitoring file handles
  *
+ * Copyright (C) 2007, 2011 Red Hat, Inc.
  * Copyright (C) 2007 Daniel P. Berrange
- * Copyright (C) 2007 Red Hat, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -140,6 +140,8 @@ void virEventRegisterImpl(virEventAddHandleFunc addHandle,
  * Once registered, the application can invoke
  * virEventRunDefaultImpl in a loop to process
  * events
+ *
+ * Returns 0 on success, -1 on failure.
  */
 int virEventRegisterDefaultImpl(void)
 {
@@ -178,6 +180,8 @@ int virEventRegisterDefaultImpl(void)
  *    if (virEventRunDefaultImpl() < 0)
  *       ...print error...
  *  }
+ *
+ * Returns 0 on success, -1 on failure.
  */
 int virEventRunDefaultImpl(void)
 {

src/util/virterror.c

@@ -1,7 +1,7 @@
 /*
  * virterror.c: implements error handling and reporting code for libvirt
  *
- * Copy:  Copyright (C) 2006, 2008-2010 Red Hat, Inc.
+ * Copy:  Copyright (C) 2006, 2008-2011 Red Hat, Inc.
  *
  * See COPYING.LIB for the License of this software
  *
@@ -1344,6 +1344,12 @@ void virReportOOMErrorFull(int domcode,
                       virerr, NULL, NULL, -1, -1, virerr, NULL);
 }
 
+/**
+ * virSetErrorLogPriorityFunc:
+ * @func: function to install
+ *
+ * Install a function used to filter error logging based on error priority.
+ */
 void virSetErrorLogPriorityFunc(virErrorLogPriorityFunc func)
 {
     virErrorLogPriorityFilter = func;