fdo#40100 make function YEARFRAC comply with ODF Version 1.2
fdo#40100 make function YEARFRAC comply with ODF Version 1.2

example of wrong result:
 =YEARFRAC(DATE(2023;1;1);DATE(2024;1;1);1)
Pretty much by definition, this should be exactly 1,
but it currently returns slightly less.

Change-Id: I5ebb2ecde49dfca8a6191d2a7c11b9581669f455

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