reduce calls to close unless error checks are needed

reduce calls to close unless error checks are needed

We can rely on timely auto-destruction based on reference
counting; reducing the chance of redundant close(2) calls
which may hit the wront FD.

We do care about certain close calls (e.g. writing to a buffered
IO handle) if we require error-checking for write-integrity.  In
other cases, let things go out-of-scope so it can be freed
automatically after use.