解决编译osgEarth中winsocket2.h找不到头文件问题

vs2013 ，需要引用以下路径，不要引用C:\Program Files (x86)\Windows Kits\8.1\Include\um这个

C:\Program Files (x86)\Microsoft SDKs\Windows\v7.1A\Include

同时确保：curlbuild.h的版本正确，要有WIN32_LEAN_AND_MEAN这个宏定义才可以

#define CURL_PULL_WS2TCPIP_H
#ifdef CURL_PULL_WS2TCPIP_H
#  ifndef WIN32_LEAN_AND_MEAN
#    define WIN32_LEAN_AND_MEAN
#  endif

#  include <winsock2.h>
#  include <windows.h>
#  include <ws2tcpip.h>
#endif