Fix gcc-4.4 testsuite failures (SF#2178663)
--- flex/flex.skl
+++ flex/flex.skl
@@ -219,6 +219,7 @@ m4preproc_include(`flexint.h')
 #include <errno.h>
 #include <cstdlib>
 #include <cstring>
+#include <cstdio>
 /* end standard C++ headers. */
 %endif