sshpeer: allow write operations through double pipe

sshpeer: allow write operations through double pipe

We have a shiny toy, lets make it wider.

--- a/mercurial/sshpeer.py	Wed May 20 17:40:47 2015 -0500
+++ b/mercurial/sshpeer.py	Wed May 20 10:58:29 2015 -0500
@@ -75,6 +75,9 @@
             act = fds
         return (self._main.fileno() in act, self._side.fileno() in act)
 
+    def write(self, data):
+        return self._call('write', data)
+
     def read(self, size):
         return self._call('read', size)
 
@@ -102,6 +105,9 @@
     def close(self):
         return self._main.close()
 
+    def flush(self):
+        return self._main.flush()
+
 class sshpeer(wireproto.wirepeer):
     def __init__(self, ui, path, create=False):
         self._url = path