Replace fileno with _fileno on Windows.
diff --git a/cmake-config.h.in b/cmake-config.h.in
index cea5d0d..81d9ebd 100644
--- a/cmake-config.h.in
+++ b/cmake-config.h.in
@@ -3,6 +3,7 @@
 #cmakedefine HAVE__CLOSE
 #cmakedefine HAVE__DUP
 #cmakedefine HAVE__FDOPEN
+#cmakedefine HAVE__FILENO
 #cmakedefine HAVE__OPEN
 #cmakedefine HAVE__SNPRINTF
 #cmakedefine HAVE__STRCMPI