Rework on TEXTE_PCB, SCH_TEXT and EDA_TextStruct classes.

Code seriously cleaned, obscure and duplicated code removed, and some oddities removed.
Better support of multiline texts.

eeschema/onrightclick.cpp

@@ -441,7 +441,11 @@ void AddMenusForText( wxMenu* PopMenu, SCH_TEXT* Text )
     ADD_MENUITEM( PopMenu, ID_POPUP_SCH_EDIT_TEXT, _( "Edit Text" ), edit_text_xpm );
     ADD_MENUITEM( PopMenu, ID_POPUP_SCH_DELETE, _( "Delete Text" ), delete_text_xpm );
 
-    // add menu change type text (to label, glabel, text):
+    /* add menu change type text (to label, glabel, text),
+     * but only if this is a single line text
+     */
+    if( Text->m_Text.Find( wxT("\n") ) ==  wxNOT_FOUND )
+    {
         ADD_MENUITEM( menu_change_type, ID_POPUP_SCH_CHANGE_TYPE_TEXT_TO_LABEL,
                       _( "Change to Label" ), label2text_xpm );
         ADD_MENUITEM( menu_change_type, ID_POPUP_SCH_CHANGE_TYPE_TEXT_TO_HLABEL,
@@ -450,6 +454,7 @@ void AddMenusForText( wxMenu* PopMenu, SCH_TEXT* Text )
                       _( "Change to Glabel" ), label2glabel_xpm );
         ADD_MENUITEM_WITH_SUBMENU( PopMenu, menu_change_type,
                                    ID_POPUP_SCH_CHANGE_TYPE_TEXT, _( "Change Type" ), gl_change_xpm );
+    }
 }