added a visitor for Set objects
Informix versions < 10 use 'FIRST' keyword instead of 'LIMIT'
Still supported in versions 10+
Merge pull request #137 from dimko/visit_set

Added a visitor for Set objects
Merge pull request #167 from pparidans/informix-v9-support

Informix versions < 10 use 'FIRST' keyword instead of 'LIMIT'
Fix set visiting spec
Merge pull request #317 from dimko/patch-2

Fix set visiting spec
connections should cache these values, so remove the cache in arel
move the dispatch table to be per-instance

visitors are not shared among threads, so any mutations to the cache
should be OK.  The cache is also pre-populated on construction, but we
should pull that out so we can share the cache among visitors in the
future.
{Matches,DoesNotMatch} support the ESCAPE clause
Merge pull request #318 from tamird/match-escape

{Matches,DoesNotMatch} support the ESCAPE clause
`Expresssions` => `Expressions` [ci skip]
Merge pull request #324 from vipulnsward/cte

`Expresssions` => `Expressions`
Reuse `maybe_visit` method

This commit simply removes duplicated code by reusing the
existing `maybe_visit` method.
Merge pull request #325 from claudiob/reuse-maybe-visit-method

Reuse `maybe_visit` method
Completes 08e6491 in reusing `maybe_visit`

:sweat: I don't know why the tests did not fail, but to keep
the same syntax as before, `collector =` is required.

Maybe `visit` changes `collector` in-place, so the result is the
same, but since I'm not sure about the side effects, I think this
PR is needed to. Sorry! :sweat:
Merge pull request #326 from claudiob/reuse-maybe-visit

Completes 08e6491 in reusing `maybe_visit`
Handle BigDecimal Ranges