[Bug-readline] readline.h dependency on stdio.h

[serge Guelton]

Hi folks,
An autoconf test on readline function recently failed due to the
following problem:

The following code (yes it is a one liner :p)

==================================
#include <readline/readline.h>
==================================

Fails to compile with gcc -c due to a dependency on stdio.h (missing
FILE definition)
This dependency did not exist before.

I am using libreadline version 6.2.001-1 from archlinux.

As of the fix, it is straight forward...

Thanks a lot !

-- serge guelton