* Pathway taken by xml-rpc call involving base64

  in Client.hs:

  + remote
    + remote_: collects up arguments + converts them all to Value
      using toValue.  In the case of an explicit ValueBase64 constructor
      this does nothing.
      + call: packages up method and args into MethodCall and calls
	+ doCall
          + renders MethodCall with 'renderCall', resulting in a lazy
            bytestring req, which is given to 'post'.
	+ handleResponse

  in Internals.hs:

  + renderCall
    + toXRMethodCall: transform MethodCall into type auto-generated by
      HaXml?  Mostly just wrapper except for toXRParams
      + toXRParams: map
	+ toXRValue: this actually does constructor-by-constructor
          translation, taking typed things into all strings. In the
          case of ValueBase64 it calls
	  + showBase64: actually does base64 encoding.
	  
      
    + showXml'