util/find-doc-nits: check podchecker() return value
From the Pod::Checker manual:
> RETURN VALUE
>        podchecker returns the number of POD syntax errors found or
>        -1 if there were no POD commands at all found in the file.
@@ -778,7 +778,8 @@ sub check {
open my $OUT, '>', $temp
or die "Can't open $temp, $!";
- podchecker($filename, $OUT);
+ err($id, "POD errors")
+ if podchecker($filename, $OUT) != 0;
close $OUT;
open $OUT, '<', $temp
or die "Can't read $temp, $!";
