Refactor comparison operators for DateTime and Time classes

Change-Id: Ia59373da6717c8705c96eecb0f1dc0016cd2dcd6
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/181068
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>
Tested-by: Jenkins

include/tools/datetime.hxx

@@ -71,9 +71,8 @@ public:
 
     auto            operator <=>( const DateTime& rDateTime ) const
                     {
-                        if (auto cmp = Date::operator<=>(rDateTime); cmp != 0)
-                            return cmp;
-                        return tools::Time::operator<=>(rDateTime);
+                        return std::make_pair(GetDate(), GetTime()) <=>
+                            std::make_pair(rDateTime.GetDate(), rDateTime.GetTime());
                     }
     bool            operator==(const DateTime& rDateTime) const
                     {

include/tools/time.hxx

@@ -133,8 +133,6 @@ public:
 
     bool            IsEqualIgnoreNanoSec( const tools::Time& rTime ) const;
 
-    bool            operator==(const Time& rTime) const = default;
-
     auto            operator <=> ( const Time& rTime ) const = default;
 
     static Time     GetUTCOffset();