year-view: Mark working days according to locale

Currently, on the year view, Saturday and Sunday are marked
as non working days by default, despite the Locale settings and the
fact that in some Countries Sunday and/or Saturday are workdays.

This patch introduces a new function "is_workday" to check
whether a day is a working day according to the territory part of
Locale.

https://bugzilla.gnome.org/show_bug.cgi?id=746927

src/gcal-utils.h

@@ -54,6 +54,18 @@ typedef enum
   GCAL_WINDOW_VIEW_SEARCH,
 } GcalWindowViewType;
 
+typedef enum
+{
+    GCAL_WEEK_DAY_INVALID   = 0,
+    GCAL_WEEK_DAY_SUNDAY    = 1 << 0,
+    GCAL_WEEK_DAY_MONDAY    = 1 << 1,
+    GCAL_WEEK_DAY_TUESDAY   = 1 << 2,
+    GCAL_WEEK_DAY_WEDNESDAY = 1 << 3,
+    GCAL_WEEK_DAY_THURSDAY  = 1 << 4,
+    GCAL_WEEK_DAY_FRIDAY    = 1 << 5,
+    GCAL_WEEK_DAY_SATURDAY  = 1 << 6
+} GcalWeekDay;
+
 GType           icaltime_get_type                               (void)            G_GNUC_CONST;
 
 gint            datetime_compare_date                           (GDateTime             *dt1,
@@ -143,4 +155,6 @@ gboolean        ask_recurrence_modification_type                (GtkWidget
                                                                  ECalObjModType        *modtype,
                                                                  ESource               *source);
 
+gboolean        is_workday                                      (guint	                day);
+
 #endif // __GCAL_UTILS_H__