bindStruct中在for循环里面进行header取数，会有内存和性能问题，可以统一放到外部处理

[KunWang2]

func (b *Binding) bindStruct(structPointer interface{}, structValue reflect.Value, req Request, pathParams PathParams) (hasVd bool, err error) {
recv, err := b.getOrPrepareReceiver(structValue)
if err != nil {
return
}

expr, err := b.vd.VM().Run(structValue)
if err != nil {
	return
}

bodyCodec, bodyBytes, err := recv.getBodyInfo(req)
if len(bodyBytes) > 0 {
	err = b.prebindBody(structPointer, structValue, bodyCodec, bodyBytes)
}
if err != nil {
	return
}
bodyString := ameda.UnsafeBytesToString(bodyBytes)
postForm, err := req.GetPostForm()
if err != nil {
	return
}
var fileHeaders map[string][]*multipart.FileHeader
if _req, ok := req.(requestWithFileHeader); ok {
	fileHeaders, err = _req.GetFileHeaders()
	if err != nil {
		return
	}
}
queryValues := recv.getQuery(req)
cookies := recv.getCookies(req)
headers := req.GetHeader()

for _, param := range recv.params {
	for i, info := range param.tagInfos {
		var found bool
		switch info.paramIn {
		case raw_body:
			err = param.bindRawBody(info, expr, bodyBytes)
			found = err == nil
		case path:
			found, err = param.bindPath(info, expr, pathParams)
		case query:
			found, err = param.bindQuery(info, expr, queryValues)
		case cookie:
			found, err = param.bindCookie(info, expr, cookies)
		case header:
			found, err = param.bindHeader(info, expr, headers)
		case form, json, protobuf:
			if info.paramIn == in(bodyCodec) {
				found, err = param.bindOrRequireBody(info, expr, bodyCodec, bodyString, postForm, fileHeaders,
					recv.hasDefaultVal)
			} else if info.required {
				found = false
				err = info.requiredError
			}
		case default_val:
			found, err = param.bindDefaultVal(expr, param.defaultVal)
		}
		if found && err == nil {
			break
		}
		if (found || i == len(param.tagInfos)-1) && err != nil {
			return recv.hasVd, err
		}
	}
}
return recv.hasVd, nil

}