Enhance request: set HTTP header in SOAP request

[Charles Chan <ch...@au1.ibm.com>]

For integrating with legacy application, we need to have a custom HTTP
header goes with the SOAP request. We found that the current implementation
of org.apache.soap.transport.http.SOAPHTTPConnection::send() already has a
parameter (headers) to accept the desired HTTP headers.

      public void send (URL sendTo, String action, Hashtable headers,
            Envelope env, SOAPMappingRegistry smr, SOAPContext ctx)

All we need is to have another org.apache.soap.rpc.Call::invoke() method
that takes a parameter (hashtable) for HTTP headers, and passes this
parameter to the one in SOAPHTTPConnection::send(), rather than a null
(which is what the current version does).

We're hopping the developer of the org.apache.soap.rpc.Call can add this
functionality to the next version of SOAP API. Thanks for your concerns.

Regards,
Charles.