Stores attributed text for display in a ObjGtk text. They can share to several text objects, if any
An associated table (GtkTextTagTable) created automatically.
_channel_ : Chn : any channel
_table_tag_ : ObjGtkTextTableTag : a table tag to integrate to the textbuffer. Can be nil to use the default and empty table.
Return : ObjGtkTextBuffer : the new object of nil if error