Fix Issue 57: we cannot simply add offsets to a void *.
Fix Issue 57: we cannot simply add offsets to a void *.

* outgoing.c:
  (socket_writev): cast iov_base properly, in order to increment it
  
Patch by: dongsheng song

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