[Eva] Tests the file tests/nonlin.c with the option -warn-special-float none.

Previous commits have introduced the new runs (and oracles) without this option.
This commit only contains the changes due to this option:
- no alarms for non-finite floating-point values.
- in the function [around_zeros], no reduction of the variable [f] as the
  division by 0 simply computes ∞.
- volatile floating-point variables have a value in [-∞..∞] ∪ NaN.