Optimization of ResultSet.next() [JDBC633]

[firebird-automations]

Submitted by: @mrotteveel

Only attempting to close fields that are actually closeable provides a minor performance improvement for calls to `ResultSet.next()` (very simple profiling showed 3-5% for non-cached TYPE_FORWARD_ONLY, 80-90% for cached/scrollable).

Pull request: #34

Commits: 1f55d28

[firebird-automations]

Modified by: @mrotteveel

Fix Version: Jaybird 5 [ 10871 ]

[firebird-automations]

Commented by: @mrotteveel

Pull request merged. Needs to be documented in release notes.

[mrotteveel]

Documented in release notes