Fix libio/bug-ungetwc1.c warning

[Ondřej Bílka]

On Wed, Nov 26, 2014 at 06:26:01PM +0000, Joseph Myers wrote:
> This patch fixes a warning "variable 'wc' set but not used" in
> libio/bug-ungetwc1.c.
> 
> The test didn't verify much about the results of the functions it
> called.  This patch makes it check the result of getwc (thereby fixing
> the warning), check end of file does not arrive too late in the getwc
> loop, and check EOF is no longer set after ungetwc.
> 
> Tested for x86_64.
> 
looks ok.