Add a missing #include.

winshare.c uses make_private_security_descriptor(), but wasn't
including winsecur.h where it's declared.

windows/winshare.c

@@ -15,6 +15,7 @@
 #include "ssh.h"
 
 #include "wincapi.h"
+#include "winsecur.h"
 
 #ifdef COVERITY
 /*