add support for timed-operations (wait_for/wait_until)

src/recursive_mutex.cpp

@@ -94,7 +94,20 @@ recursive_mutex::lock()
 bool
 recursive_mutex::try_lock()
 {
-    if ( LOCKED == state_) return false;
+    if ( LOCKED == state_)
+    {
+        if ( this_fiber::get_id() == owner_)
+        {
+            ++count_;
+            return true;
+        }
+        else
+        {
+            // let other fiber release the lock
+            detail::scheduler::instance()->yield();
+            return false;
+        }
+    }
 
     state_ = LOCKED;
     owner_ = this_fiber::get_id();