Changes compared to version 2.2

o  Fix yet another print using bug
o  LIST may be aborted with ^C
o  Added the $ format specifier to print using
o  DELETE can take a range
o  Only output copyright notice and prompt if input is a tty
o  Restore terminal attributes before SHELL
o  Ignore SIGINT and SIGQUIT during execution of subshells
o  Let a line number with empty line delete a line
o  DELETE bug fixed
o  Allow mid$()=val to be use any place where an assignment is used
o  END gives a diagnostic message and does not crash if used interactively
   without a program
o  Added MAT WRITE
o  SAVE remembers the argument like LOAD does
o  Multi assignments
o  Remove \r when reading a file
