Preserve nil <-> NULL between Nimrod and database.
Merge branch 'devel' of github.com:Araq/Nimrod into devel

Merging mainline devel.
Merge branch 'devel' of github.com:Araq/Nimrod into devel

Merging mainline devel.
Merge branch 'devel' of github.com:Araq/Nimrod into devel

Merging mainline devel.
Tweaks for postgres driver (not tested yet).
Merge branch 'devel' of github.com:Araq/Nimrod into devel
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Merge pull request #1497 from milosn/devel

Preserve nil <-> NULL between Nimrod and database.