Added distvariance sound parameter to sound scripts, allowing for distance blending to be tweaked instead of being tied to a cvar. Usage is distvariance "near, far"
Re-enabled the following operators in the math_float sound operator: asinh, atanh, acosh, expm1, expm2, log2, log1p, logb, erf, erfc, gamma, lgamma, rint, nearbyint, roundtol and trunc