port libcurl to wince

libcurl is a powerful network transfer library. It has support for many popular protocols and can make our application easier to integrate with other network servers.
libcurl requires some posix headers to compile, which isn't available on windows ce platform. In order to port it, we must provide a  posix adapter layer, which can be achieved with wcecompat library.
It's not enough to only have wcecompat library, because the source code of libcurl isn't fully wince compatible. We can apply this patch to libcurl source code to make it compile fine.