A first partial implementation of deleting is introduced. The user might

A first partial implementation of deleting is introduced. The user might
want to delete in two ways: a deleting mode near to what he has actually
typed (textual mode) and a deleting mode near to what screen shows (graphical
mode). Only a partial implementation of the second mode is provided. The user
can delete a macro he is typing, a group, an identifier, a number, a
superscript and a subscript. To delete in graphical mode the user has to type
BACKSPACE.
Added the following private methods to TPushParser class:
  void do_gdelete(void)
  void gdelete_prev(void)
Added the entry GDELETE to the TCat enum defined in the TToken struct.