core.async: add send() method and 'sent' property

gevent/core.ppyx

@@ -747,6 +747,13 @@ cdef public class async(watcher) [object PyGeventAsyncObject, type PyGeventAsync
 
     INIT(async,,)
 
+    def send(self):
+        libev.ev_async_send(self.loop._ptr, &self._watcher)
+
+    @property
+    def sent(self):
+        return libev.ev_async_pending(&self._watcher)
+
 
 #cdef public class child(watcher) [object PyGeventChildObject, type PyGeventChild_Type]:
 #

gevent/libev.pxd

@@ -131,6 +131,8 @@ cdef extern from "libev.h":
     void ev_async_init(ev_async*, void* callback)
     void ev_async_start(ev_loop*, ev_async*)
     void ev_async_stop(ev_loop*, ev_async*)
+    void ev_async_send(ev_loop*, ev_async*)
+    int ev_async_pending(ev_async*)
 
     void ev_child_init(ev_child*, void* callback, int, int)
     void ev_child_start(ev_loop*, ev_child*)