Chain @return types

[blaaat]

For Chaining ->assign('x',1)->displa('x'); and IDE/static analysis purposes can I suggest having the proper @return docblock?

so for example:
* @return static current Smarty_Internal_Data (or Smarty or Smarty_Internal_Template) instance for * chaining

instead of:

* @return Smarty_Internal_Data current Smarty_Internal_Data (or Smarty or Smarty_Internal_Template) instance for chaining

[wisskid]

@blaaat could you provide a PR?