Revert "i2smo: add brackets as invalid chars for name"

This reverts commit 013445da.

+ parentheses in param names break RPN formulas, so if we don't use a param in a RPN formula, we should be fine
+ if we use a param name containing parentheses in a RPN formula in <defined> or <drawdefinable> section, i2smo will emit and error anyway, as ipk2szarp will fail on parsing formula
+ it's not practical to enforce this rule on existing configurations as lots of params exist on existing SZARP sites and i2smo prints lots of confusing errors then