[dev][sbase] cal improvements

[Krol, Willem van de]

Good evening,

Attached are two patches. The first is to optimize the leap year
calculation, and the second patch changes the dayofweek algorithm to
fix the handling of a different first day of the week (that is, fday
!= 0).

Sincerely,
Willem

0001-optimized-isleap-function.patch
Description: Binary data

0002-fixed-incorrect-fday-handling-in-dayofweek-function.patch
Description: Binary data