Upgrade gin-gonic to latest master, fix compatibility issues

vendor/github.com/gin-gonic/gin/binding/form.go

@@ -0,0 +1,54 @@
+// Copyright 2014 Manu Martinez-Almeida.  All rights reserved.
+// Use of this source code is governed by a MIT style
+// license that can be found in the LICENSE file.
+
+package binding
+
+import "net/http"
+
+type formBinding struct{}
+type formPostBinding struct{}
+type formMultipartBinding struct{}
+
+func (formBinding) Name() string {
+	return "form"
+}
+
+func (formBinding) Bind(req *http.Request, obj interface{}) error {
+	if err := req.ParseForm(); err != nil {
+		return err
+	}
+	req.ParseMultipartForm(32 << 10) // 32 MB
+	if err := mapForm(obj, req.Form); err != nil {
+		return err
+	}
+	return validate(obj)
+}
+
+func (formPostBinding) Name() string {
+	return "form-urlencoded"
+}
+
+func (formPostBinding) Bind(req *http.Request, obj interface{}) error {
+	if err := req.ParseForm(); err != nil {
+		return err
+	}
+	if err := mapForm(obj, req.PostForm); err != nil {
+		return err
+	}
+	return validate(obj)
+}
+
+func (formMultipartBinding) Name() string {
+	return "multipart/form-data"
+}
+
+func (formMultipartBinding) Bind(req *http.Request, obj interface{}) error {
+	if err := req.ParseMultipartForm(32 << 10); err != nil {
+		return err
+	}
+	if err := mapForm(obj, req.MultipartForm.Value); err != nil {
+		return err
+	}
+	return validate(obj)
+}