Sync with upstream

Even though libgd/libgd#492 is not a relevant bug fix for PHP, since
the binding doesn't use the `gdImage*Ptr()` functions at all, we're
porting the fix to stay in sync here.
int gd_getin (void *in)
{
 	return (gdGetC((gdIOCtx *) in));
 }

int gd_getin (void *in)
{
 	return (gdGetC((gdIOCtx *) in));
 }
