math: regenerate all math tests
    
    gen used exp range limitation to get ieee semantics but
    mpfr seems to have problems with it (eg gamma(next(-180))
    incorrectly underflows) so different strategy is used:
    use full exp range and only narrow it before converting
    the result
    
    now the error term uses nearest rounding and sign difference
    is treated as inf ulp error during tests
    
    added helper tools to convert between float formats