Add key "unique" to history_request protocol

IPython/kernel/zmq/ipkernel.py

@@ -504,9 +504,10 b' class Kernel(Configurable):'
 
         elif hist_access_type == 'search':
             n = parent['content'].get('n')
+            unique = parent['content'].get('unique')
             pattern = parent['content']['pattern']
-            hist = self.shell.history_manager.search(pattern, raw=raw,
-                                                     output=output, n=n)
+            hist = self.shell.history_manager.search(
+                pattern, raw=raw, output=output, n=n, unique=unique)
 
         else:
             hist = []