Revert "Include signal.h for sig_atomic_t in WIN32"

This reverts commit 88f14b999c.

src/util.h

@@ -28,7 +28,9 @@
 #include <boost/signals2/signal.hpp>
 #include <boost/thread/exceptions.hpp>
 
+#ifndef WIN32
 #include <signal.h>
+#endif
 
 static const bool DEFAULT_LOGTIMEMICROS = false;
 static const bool DEFAULT_LOGIPS        = false;