util: explicitly include windows.h

The virProcess code relies on windows.h and is getting it
indirectly via some GNULIB header fixes. This dependancy
needs to be made explicit.
Reviewed-by: NPavel Hrdina <phrdina@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

src/util/virprocess.c

@@ -50,6 +50,11 @@
 # include <sys/cpuset.h>
 #endif
 
+#ifdef WIN32
+# define WIN32_LEAN_AND_MEAN
+# include <windows.h>
+#endif
+
 #include "viratomic.h"
 #include "virprocess.h"
 #include "virerror.h"