simplify some code by using scintilla internal commands * file-editor-tab.cc (undo, redo, copy, cut, selectall): remove * file-editor-tab.h: remove undo, redo, copy, cut, selectall * file-editor.cc (request_undo, request_redo, request_copy, request_cut, request_paste, reuqest_selectall): replace particular signal by common signal that sends the scintilla command as paramter; (add_new_edit_tab): remove the connects of the obsolete signals * file-editor.h: remove obsolete signals

gnulib-hg = gnulib-hg