Fix compatibility issue with HTTPMessage class.

The server needs to use MessageClass to parse.
diff --git a/Lib/http/server.py b/Lib/http/server.py
index 897908e..31153f4 100644
--- a/Lib/http/server.py
+++ b/Lib/http/server.py
@@ -313,7 +313,8 @@
         self.command, self.path, self.request_version = command, path, version
 
         # Examine the headers and look for a Connection directive.
-        self.headers = http.client.parse_headers(self.rfile)
+        self.headers = http.client.parse_headers(self.rfile,
+                                                 _class=self.MessageClass)
 
         conntype = self.headers.get('Connection', "")
         if conntype.lower() == 'close':