Cache resolved SPN for SSPI-based Negotiate authentication.
Cache resolved SPN for SSPI-based Negotiate authentication.

* auth/auth_spnego_sspi.c
  (serf__spnego_context_t): Add POOL and TARGET_NAME.
  (serf__spnego_create_sec_context): Initialize POOL and TARGET_NAME.
  (serf__spnego_init_sec_context): Initialize ctx->TARGET_NAME if not 
   initialized and use it if already it known.

muthusuba/serf,sworda/serf,blueszhangsh/serf,blueszhangsh/serf,krime/serf,blueszhangsh/serf,TommyU/serf,Manouchehri/serf,justinweb/serf,wzugang/serf,sworda/serf,Manouchehri/serf,blueszhangsh/serf,wzugang/serf,TommyU/serf,Manouchehri/serf,muthusuba/serf,liuzongquan/serf,idomon/serf,sworda/serf,idomon/serf,TommyU/serf,wzugang/serf,TommyU/serf,justinweb/serf,liuzongquan/serf,Manouchehri/serf,liuzongquan/serf,justinweb/serf,justinweb/serf,idomon/serf,wzugang/serf,muthusuba/serf,muthusuba/serf,krime/serf,krime/serf,idomon/serf,sworda/serf,liuzongquan/serf,krime/serf