This provides the same functionality as `$` proc, but it keeps working
with Nim 1.3+, where `parseEnum` implementation has been changed to be
able to work with enums with holes (after a bugfix for them).
Note that the first character is case-sensitive and "Constantinople" !=
"constantinople".
Since the tests (`test_op_arith` and `test_op_bit`) use lower-case first
letter, the string representation is also changed to the lower-case.
36a75197d2