[7929] Some fixes and optimizations for work with packet guids. Author: VladimirMangos

* Allocate only minimal required buffer size for object packet guid cache, avoid it realocation.
    * At adding aboyher buffer content copy only until wpos (really writed to buffer data)
    * In appendPackGUID check buffer size before data write.

--HG--
branch : trunk

src/shared/ByteBuffer.h

@@ -311,11 +311,14 @@ class ByteBuffer
         }
         void append(const ByteBuffer& buffer)
         {
-            if(buffer.size()) append(buffer.contents(),buffer.size());
+            if(buffer.size()) append(buffer.contents(),buffer.wpos());
         }
 
         void appendPackGUID(uint64 guid)
         {
+            if (_storage.size() < _wpos + sizeof(guid) + 1)
+                _storage.resize(_wpos + sizeof(guid) + 1);
+
             size_t mask_position = wpos();
             *this << uint8(0);
             for(uint8 i = 0; i < 8; i++)