Generating correct LIMIT and OFFSET field names

[dominikbraun]

Fixes #201.

A query like this caused incorrect field names for LIMIT and OFFSET:

-- name: GetFoo :one
SELECT
    (SELECT 1) AS baz
FROM foo
WHERE
	bar = $1
LIMIT $2
OFFSET $3;

The generated struct used to look like this:

type GetFooParams struct {
	Bar   string `json:"bar"`
	Bar_2 string `json:"bar_2"`
	Bar_3 string `json:"bar_3"`
}

This happened because LIMIT and OFFSET are nil for the subquery but they've been assigned to the paramSearch though.

[kyleconroy]

@dominikbraun Thanks for the pull request. I think the existing limit / offset code needs to be totally rewritten. For example I don't think the following query will compile correctly:

-- name: GetFoo :one
WITH cte as (
    SELECT foo FROM bar LIMIT $1
)
SELECT
foo
FROM cte
OFFSET $2;

[dominikbraun]

Yap, and while (SELECT 1) AS baz works as a subquery for the query shown above, (SELECT 1 FROM foo) AS baz runs into an error:

column reference "bar" is ambiguous

You may merge this PR as a temporary hotfix, or just rewrite the affected code from scratch.

[kyleconroy]

You may merge this PR as a temporary hotfix

Since I'm not sure about the long-term fix, adding a hot fix seems like a fine approach.