Fix a compile error on JS target (fix #50)

[jgranick]

Using an optional function parameter of a basic type (such as Bool) results in compile errors.

For example, adding to the Calculator mock example:

public function add (value1:Float, value2:Float, _round:Bool = false):Float {
    if (_round) return round(value1 + value2);
    return value1 + value2;
}

Results in this error:

src/math/Calculator.hx:13: lines 13-16 : Field add overloads parent class with different or incomplete type
src/math/Calculator.hx:13: lines 13-16 : value : Float -> value2 : Float -> ?_round : Null<Bool> -> Float should be value : Float -> value2 : Float -> ?_round : Bool -> Float
src/math/Calculator.hx:13: lines 13-16 : Null<Bool> should be Bool

Returning null as the default parameter on all dynamic targets for macro.tools.ComplexTypes results in forcing type Bool to be Null<Bool>, but this was not the original type. On current Haxe development builds, this is the error, on Haxe 3.2.1 it printed "src/Main.hx:28: characters 15-25 : math.CalculatorMocked has no field round" which is more confusing.

Removing the Tools.isStaticPlatform() conditional seems to fix this condition on JavaScript.