program: removed rpn list from line info list

the translated rpn lists for program lines were being saved so that they
could be used to detect when a line changed by comparing the rpn list
for the line with the translated rpn list of the new line; these saved
rpn lists are no longer needed since the actual program code of the line
can be decoded into an rpn list and this can be compared

removed the rpn list variable from the line info structure along with
all references to it; for the line change detection, the rpn list for
the line to check is now obtained from the decode function (the returned
rpn list is deleted after comparing to the incoming rpn list)

corrected the comparison of the token string for tokens other than the
rem and constant string codes to do a case insensitive string compare
(the default case sensitive option was incorrectly being used)