function layout(view){
  this.locals._layoutFile = view;
}
Apply the given `view` as the layout for the current template,
using the current options/locals. The current template will be
supplied to the given `view` as `body`, along with any `blocks`
added by child templates.

`options` are bound  to `this` in renderFile, you just call
`layout('myview')`

@param  {String} view
@api private