BindQuery not support pointer

[Jiachang-Cai]

`
package main

import (
"github.com/gin-gonic/gin"
"net/http"
)

type User struct {
UserName *string form:"user_name" binding:"required"
}

func main() {
r := gin.Default()
r.GET("/user", getUser)
r.Run(":8085")
}

func getUser(c *gin.Context) {
var user User
if err := c.BindQuery(&user); err == nil {
c.JSON(http.StatusOK, gin.H{"message": "valid!"})
} else {
c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
}
}
`

[ziyoumeng]

Because release v1.2 not support BindQuery，you should get newest code.

[thinkerou]

Implement in #1336 . try it in the latest master branch.