Add changes and new methods from libxl 3.5.4, enable excel file type setting

Hi, like you recommend I have done the changes you requested.
- please, add a test case
- I  use an Int, for setting an XML book, as an optional parameter. 
  Also add constant BOOK_XLS and BOOK_XLSX for the Int.
- update docs was not possible. The don't exist.
- keep indentations
- make a different pull request