Turn off close() warnings on bad filehandles when exceptions are on.

[schwern]

close will warn in some cases, like if it's given a bad filehandle. This is redundant with exceptions on. Turn it off if exceptions are on.

The code is in report_evil_fh in util.c. This code is used in multiple places, including do_close. report_evil_fh could be made to throw, but errno is set afterwards in do_close.