No real changes, just cleanup week days handling in wxGenericCalendarCtrl.

Use helper GetWeek{Start,End}() functions instead of repeating tests for
wxCAL_MONDAY_FIRST over and over again.

Also replace some occurrences of GetWindowStyle() with shorter and more clear
HasFlag().

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65902 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/generic/calctrlg.h

@@ -199,6 +199,20 @@ private:
     // get the date from which we start drawing days
     wxDateTime GetStartDate() const;
 
+    // get the first/last days of the week corresponding to the current style
+    wxDateTime::WeekDay GetWeekStart() const
+    {
+        return HasFlag(wxCAL_MONDAY_FIRST) ? wxDateTime::Mon
+                                           : wxDateTime::Sun;
+    }
+
+    wxDateTime::WeekDay GetWeekEnd() const
+    {
+        return HasFlag(wxCAL_MONDAY_FIRST) ? wxDateTime::Sun
+                                           : wxDateTime::Sat;
+    }
+
+
     // is this date shown?
     bool IsDateShown(const wxDateTime& date) const;