table: removed code enumerator in-line increment functions

changed operators to sub-string assignment operators so that they match
the base sub-string functions; this allows the assign string recreate
function to not have to search for the base sub-string function code

removed using -1 as second associated index of sub-string functions
removed negative second associated index change from set token code
  (this function is not used for sub-string functions)
added ASC2, INSTR3, MID3 as second associated code to ASC, INSTR2, MID2
changed translator to use second associated code for multiple codes
removed token next code access function