ActiveSync: implemented TestingSyncSource::deleteAll()

The default implementation removes one VEVENT after the other, which
is slow for large merged events. Directly removing the entire event
series is faster.

src/backends/activesync/ActiveSyncCalendarSource.cpp

@@ -639,6 +639,14 @@ void ActiveSyncCalendarSource::deleteItem(const string &luid)
     }
 }
 
+void ActiveSyncCalendarSource::removeAllItems()
+{
+    BOOST_FOREACH(const EventCache::value_type &entry, m_cache) {
+        ActiveSyncSource::deleteItem(entry.first);
+    }
+    m_cache.clear();
+}
+
 std::string ActiveSyncCalendarSource::createLUID(const std::string &uid, const std::string &subid)
 {
     std::string luid = m_escape.escape(uid);

src/backends/activesync/ActiveSyncCalendarSource.h

@@ -69,6 +69,9 @@ class ActiveSyncCalendarSource : public ActiveSyncCalFormatSource
     /** split luid into uid (first) and rid (second) */
     static StringPair splitLUID(const std::string &luid);
 
+    // more efficient implementation than in TestingSyncSource
+    virtual void removeAllItems();
+
  private:
     /** compose luid from mainid and subid */
     static std::string createLUID(const std::string &uid, const std::string &rid);