message: Remove CatalogItem copy constructor
  The copy constructor is not used for anything anymore and stays in the
  way of virtualizing the interface.
diff: @@ -88,25 +88,7 @@ class CatalogItem
  m_lineNum(0),
  m_bookmark(NO_BOOKMARK) {}
  - CatalogItem(const CatalogItem& dt)
  - : m_id(dt.m_id),
  - m_string(dt.m_string),
  - m_plural(dt.m_plural),
  - m_hasPlural(dt.m_hasPlural),
  - m_hasContext(dt.m_hasContext),
  - m_context(dt.m_context),
  - m_translations(dt.m_translations),
  - m_references(dt.m_references),
  - m_extractedComments(dt.m_extractedComments),
  - m_oldMsgid(dt.m_oldMsgid),
  - m_isFuzzy(dt.m_isFuzzy),
  - m_isTranslated(dt.m_isTranslated),
  - m_isModified(dt.m_isModified),
  - m_isPreTranslated(dt.m_isPreTranslated),
  - m_moreFlags(dt.m_moreFlags),
  - m_comment(dt.m_comment),
  - m_lineNum(dt.m_lineNum),
  - m_bookmark(dt.m_bookmark) {}
  + CatalogItem(const CatalogItem&) = delete;
  /// Gets numeric, 1-based ID
  int GetId() const { return m_id; }
  