Currently `posts.title` is regarded as a safe SQL string, but
`"posts"."title"` (it is a result of `quote_table_name("posts.title")`)
is regarded as an unsafe SQL string even though a result of
`quote_table_name` should obviously be regarded as a safe SQL string,
since the column name matcher doesn't respect quotation, it is a little
annoying.

This changes the column name matcher to allow quoted identifiers as safe
SQL string, now all results of the `quote_table_name` are regarded as
safe SQL string.