Following up on r1448339, also make the status externals processing
completely part of the status processing.

* subversion/libsvn_client/client.h
  (svn_client__do_external_status): Remove prototype.

* subversion/libsvn_client/externals.c
  (svn_client__do_external_status): Remove function here...

* subversion/libsvn_client/status.c
  (do_external_status): ... that can just be placed here as static.
  (svn_client_status5): Update caller.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1448340 13f79535-47bb-0310-9956-ffa450edef68