Avoid output to System.err when finding unique Enum name

[joelittlejohn]

No description provided.

[unkish]

New logged out message makes more sense now also (sample from EnumIT::enumWithNoValidCharactersForIdentifier output):

Enum name __EMPTY__ already used; trying to replace it with __EMPTY___
Enum name __EMPTY___ already used; trying to replace it with __EMPTY____
Enum name __EMPTY__ already used; trying to replace it with __EMPTY____

vs.

[warn] Enum name __EMPTY__ already used; trying to replace it with __EMPTY___
[warn] Enum name __EMPTY__ already used; trying to replace it with __EMPTY___
[warn] Enum name __EMPTY___ already used; trying to replace it with __EMPTY____