As report_evil_fh() checks WARN_{CLOSED,UNOPENED}, don't duplicate this.

As report_evil_fh() checks WARN_{CLOSED,UNOPENED}, don't duplicate this.

This trades reduced code size for an extra function call in the error path with
warnings disabled. (And removes a duplicated check for the case of taking the
error path *with* warnings enabled.)

Removing the check from Perl_do_close() does not change behaviour, as io is
NULL there, hence Perl_report_evil_fh() will always be checking WARN_UNOPENED
and setting vile to "unopened".