chgserver: mark as a built-in extension

chgserver: mark as a built-in extension

--- a/hgext/chgserver.py	Wed Dec 23 22:23:56 2015 +0900
+++ b/hgext/chgserver.py	Wed Dec 23 22:37:24 2015 +0900
@@ -48,6 +48,12 @@
     util,
 )
 
+# Note for extension authors: ONLY specify testedwith = 'internal' for
+# extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
+# be specifying the version(s) of Mercurial they are tested with, or
+# leave the attribute unspecified.
+testedwith = 'internal'
+
 _log = commandserver.log
 
 # copied from hgext/pager.py:uisetup()