some small improvements for the FILTERXML function
some small improvements for the FILTERXML function

Change-Id: I4b4e814d90592f318afb3a9a6965ad8e3df07cae

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core