Fix memory leak in __printf_fp_l (bug 26215)

[Florian Weimer]

* Joseph Myers:

> __printf_fp_l has a memory leak in the case of some I/O errors, where
> both buffer and wbuffer have been malloced but the handling of I/O
> errors only frees wbuffer.  This patch fixes this by moving the
> declaration of buffer to an outer scope and ensuring that it is freed
> when wbuffer is freed.

Do we need to treat this as a securityh vulnerability?  I don't think
so, because there are no impacted applications as far as I can tell.

Thanks,
Florian