func NewLiteralExpression(sql string, args ...interface{}) LiteralExpression {
	return literal{literal: sql, args: args}
}
Creates a new SQL literal with the provided arguments.
L("a = 1") -> a = 1
You can also you placeholders. All placeholders within a Literal are represented by '?'
L("a = ?", "b") -> a = 'b'
Literals can also contain placeholders for other expressions
L("(? AND ?) OR (?)", I("a").Eq(1), I("b").Eq("b"), I("c").In([]string{"a", "b", "c"}))
package exp
type (
	literal struct {
		literal string
		args    []interface{}
	}
)