Add HAVE_FILENO so cmake detects it correctly.

cmake-config.h.in

diff --git a/cmake-config.h.in b/cmake-config.h.in
index 36f2baa..1f17631 100644
--- a/cmake-config.h.in
+++ b/cmake-config.h.in
@@ -12,6 +12,7 @@
 #cmakedefine HAVE__SNPRINTF
 #cmakedefine HAVE__STRDUP
 #cmakedefine HAVE__STRICMP
+#cmakedefine HAVE_FILENO
 #cmakedefine HAVE_FSEEKO
 #cmakedefine HAVE_FTELLO
 #cmakedefine HAVE_OPEN