Work on #7947 (CalendarView not respecting locale's start of week)

* support all weekdays as start of week, not only Sunday and Monday
  (at least Saturday is used for real, too)
* introduce BWeekday as enumeration of weekdays (currently in Locale.h,
  may be moved somewhere else later)
* change CalendarView to use BDate as its model, not individual values
  for day, month and year, such that no more date computation is done 
  in CalendarView itself
* some more style cleanups in CalendarView along the way
* add monthwise paging to CalendarView
* adjusted Deskbar and Time preflet accordingly


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42720 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/os/locale/Locale.h

@@ -22,7 +22,7 @@ class BString;
 class BTimeZone;
 
 
-typedef enum {
+enum BDateElement {
 	B_DATE_ELEMENT_INVALID = B_BAD_DATA,
 	B_DATE_ELEMENT_YEAR = 0,
 	B_DATE_ELEMENT_MONTH,
@@ -31,14 +31,26 @@ typedef enum {
 	B_DATE_ELEMENT_HOUR,
 	B_DATE_ELEMENT_MINUTE,
 	B_DATE_ELEMENT_SECOND
-} BDateElement;
+};
 
-typedef enum {
+enum BNumberElement {
 	B_NUMBER_ELEMENT_INVALID = B_BAD_DATA,
 	B_NUMBER_ELEMENT_INTEGER = 0,
 	B_NUMBER_ELEMENT_FRACTIONAL,
 	B_NUMBER_ELEMENT_CURRENCY
-} BNumberElement;
+};
+
+
+// TODO: move this to BCalendar (should we ever have that) or BDate
+enum BWeekday {
+	B_WEEKDAY_MONDAY = 1,
+	B_WEEKDAY_TUESDAY,
+	B_WEEKDAY_WEDNESDAY,
+	B_WEEKDAY_THURSDAY,
+	B_WEEKDAY_FRIDAY,
+	B_WEEKDAY_SATURDAY,
+	B_WEEKDAY_SUNDAY,
+};
 
 
 class BLocale {
@@ -99,7 +111,7 @@ public:
 									int& fieldCount, BDateFormatStyle style
 									) const;
 
-			int					StartOfWeek() const;
+			status_t			GetStartOfWeek(BWeekday* weekday) const;
 
 								// Time