trivial native mutex doc tweak.

Index: ksrc/skins/native/mutex.c
===================================================================
@@ -297,7 +297,7 @@ int rt_mutex_delete(RT_MUTEX *mutex)
  * recursive and implement the priority inheritance protocol.
  *
  * Since a nested locking count is maintained for the current owner,
- * rt_mutex_lock() and rt_mutex_unlock() must be used in pairs.
+ * rt_mutex_acquire() and rt_mutex_release() must be used in pairs.
  *
  * Tasks pend on mutexes by priority order.
  *

Index: ksrc/skins/native/snippets/mutex.c
===================================================================
@@ -17,11 +17,11 @@ int main (int argc, char *argv[])
     /* Now, grab the mutex lock, run the critical section, then
        release the lock: */
 
-    rt_mutex_lock(&mutex_desc,TM_INFINITE);
+    rt_mutex_acquire(&mutex_desc,TM_INFINITE);
 
     /* ... Critical section ... */
     
-    rt_mutex_unlock(&mutex_desc);
+    rt_mutex_release(&mutex_desc);
 
     /* ... */
 }

Index: ksrc/skins/native/snippets/cond_var.c
===================================================================
@@ -21,12 +21,12 @@ void foo (void)
 
     /* Now, wait for some task to post the shared event... */
 
-    rt_mutex_lock(&mutex_desc,TM_INFINITE);
+    rt_mutex_acquire(&mutex_desc,TM_INFINITE);
 
     while (!shared_event && !err)
 	err = rt_cond_wait(&cond_desc,&mutex_desc,TM_INFINITE);
     
-    rt_mutex_unlock(&mutex_desc);
+    rt_mutex_release(&mutex_desc);
 
     /* ... */
 }

@@ -38,12 +38,12 @@ void bar (void)
 
     /* Post the shared event. */
 
-    rt_mutex_lock(&mutex_desc,TM_INFINITE);
+    rt_mutex_acquire(&mutex_desc,TM_INFINITE);
 
     shared_event = 1;
     rt_cond_signal(&cond_desc);
 
-    rt_mutex_unlock(&mutex_desc);
+    rt_mutex_release(&mutex_desc);
 
     /* ... */
 }