for months of given years, dispatch the # of French public holidays in days of the week
[holi_saturday,holi_sunday,holi_wd]=French_holi_inwd(years_holi)
* years_holi = a (2 x 1) vector, the years bounds
* holi_saturday = a ts, collecting for each month of the given years the # of French public holidays occuring on Saturday
* holi_sunday = a ts, collecting for each month of the given years the # of holidays occuring on Sunday
* holi_wd = a ts, collecting for each month of the given years the # of holidays occuring on other days of the week