Remove unused IEventQueue::isEmpty() method to simplify code understanding

Current code base don't use IEventQueue::isEmpty() method.
Remove it to simplify IEventQueue API and to remove confusion with
IEventQueueBuffer with same name.

The IEventQueueBuffer::isEmpty() and all its implementations kept unchanged

src/lib/base/EventQueue.cpp

@@ -436,12 +436,6 @@ EventQueue::removeHandlers(void* target)
     }
 }
 
-bool
-EventQueue::isEmpty() const
-{
-    return (m_buffer->isEmpty() && getNextTimerTimeout() != 0.0);
-}
-
 IEventJob*
 EventQueue::getHandler(Event::Type type, void* target) const
 {

src/lib/base/EventQueue.h

@@ -58,7 +58,6 @@ public:
     virtual void        removeHandlers(void* target);
     virtual Event::Type
                         registerTypeOnce(Event::Type& type, const char* name);
-    virtual bool        isEmpty() const;
     virtual IEventJob*    getHandler(Event::Type type, void* target) const;
     virtual const char*    getTypeName(Event::Type type);
     virtual Event::Type

src/lib/base/IEventQueue.h

@@ -189,13 +189,6 @@ public:
     //! @name accessors
     //@{
 
-    //! Test if queue is empty
-    /*!
-    Returns true iff the queue has no events in it, including timer
-    events.
-    */
-    virtual bool        isEmpty() const = 0;
-
     //! Get an event handler
     /*!
     Finds and returns the event handler for the \p type, \p target pair