send as much as possible of the POST at once

 HTTP

 * Pass a list of host name to libcurl to which we allow the user name and

   password to get sent to. Currently, it only get sent to the host name that

   the first URL uses (to prevent others from being able to read it), but this

   also prevents the authentication info from getting sent when following

   locations to legitimate other host names.

 * If the "body" of the POST is < MSS it really aught to be sent along with

   the headers. More generally, if the last chunk of the POST body is < MSS,

   it should be sent with the previous chunk (which may be the POST headers).

   So long as any one send is larger than MSS (or there is only one send when

   < MSS :), the Nagle Algorithm will not be a problem on any stack where

   Nagle is implemented correctly. (pointed out by Rick Jones)

 * Authentication: NTLM. Support for that MS crap called NTLM

   authentication. MS proxies and servers sometime require that. Since that