QPID-4621: Arithmetic oprations for C++ broker selectors
- Added explicit lexical tokens for all the comparison and arithmetic operations
- Added the missing ',' token for us in the 'IN' comparison
- Rearranged the lexer so that everything is not uniformly inside the
  hand crafted state machine.
- Moved a bunch of testing code from the tokeniser to the unit test
  (much of this code might actually not be very useful anymore)