[http] use own files send method on Windows
[http] use own files send method on Windows

civetweb mg_send_file function does not support symbolic links on
Windows, but in some situations it is required. Advantage of
mg_send_file() that it supports partial reading, therefore keep
functionality for ROOT files
root-mirror/root,root-mirror/root,karies/root,root-mirror/root,olifre/root,root-mirror/root,karies/root,root-mirror/root,olifre/root,olifre/root,karies/root,olifre/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root,karies/root,root-mirror/root,karies/root,karies/root,karies/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root,olifre/root,karies/root,karies/root,karies/root,karies/root