fix: batch insert bind for ptr slice

[fifsky]

Variables behave inconsistently when using batch inserts

  people := []Person{}
  db.Select(&people, "SELECT * FROM person ORDER BY first_name ASC")   <---- this is ptr

  // batch insert with structs
  personStructs := []Person{
      {FirstName: "Ardie", LastName: "Savea", Email: "asavea@ab.co.nz"},
      {FirstName: "Sonny Bill", LastName: "Williams", Email: "sbw@ab.co.nz"},
      {FirstName: "Ngani", LastName: "Laumape", Email: "nlaumape@ab.co.nz"},
  }

  _, err = db.NamedExec(`INSERT INTO person (first_name, last_name, email)
      VALUES (:first_name, :last_name, :email)`, personStructs) <----- this not ptr

So, support batch insert used ptr slice

  // batch insert with structs
  personStructs := []Person{
      {FirstName: "Ardie", LastName: "Savea", Email: "asavea@ab.co.nz"},
      {FirstName: "Sonny Bill", LastName: "Williams", Email: "sbw@ab.co.nz"},
      {FirstName: "Ngani", LastName: "Laumape", Email: "nlaumape@ab.co.nz"},
  }

  _, err = db.NamedExec(`INSERT INTO person (first_name, last_name, email)
      VALUES (:first_name, :last_name, :email)`, &personStructs) <----- this ptr

[dlsniper]

Hello, @ardan-bkennedy, and I recently stepped in to help maintain this project.
We are sorting the opened issues and pull requests and would like to know if you still NEED this merged.
Thank you for your contribution.