corrected input prompt error detection in old translator

with certain types of the string expressions error in the prompt in the
INPUT PROMPT command would cause a segmentation fault because the first
and last tokens were not being handled properly

since no test statements caught this problem, several statements were
added to translator test #12 (INPUT commands) to test these error
conditions
implemented more fully functional done item/stack classes

done stack class has its own header and source file
new pop function deletes any parentheses tokens in first/last operands
new drop function deletes any parentheses tokens in first/last operands
new replaceTopFirstLast() function to replaced first/last operands on
  top of done stack

moved deleteOpenParen() and deleteCloseParen() functions from translator
  to done item class (with static versions to handle any token and
  member versions to handle first/last token members)
new replaceFirst() and replaceLast() for replacing first/last token
  pointers deleting and open/close parenthesis tokens present

removed Translator::doneStackPopToken() function