Spectator - Fix BIS_fnc_lerp causing crash in 3rd person spectator

[PabstMirror]

Using 3rd person follow in spectator caused hard game crash.
It pushed camera out to infinity

TRACE: 9649 pre1: _zoom=1, _zoomTemp=-3.48678e+009 z\ace\addons\spectator\functions\fnc_cam_prepareTarget.sqf:28
TRACE: 9649 pre2: ace_spectator_camDistance=1, ace_spectator_camDistanceTemp=-3.48678e+009 z\ace\addons\spectator\functions\fnc_cam_prepareTarget.sqf:29
TRACE: 9649 new: ace_spectator_camDeltaTime=0.171005, _zoomTemp=3.13811e+010 z\ace\addons\spectator\functions\fnc_cam_prepareTarget.sqf:34
TRACE: 9649 x: _bbd=[1.6,2.2,2], _distance=3.13811e+010 z\ace\addons\spectator\functions\fnc_cam_prepareTarget.sqf:40

1.78 changed BIS_fnc_lerp, both files still exist but the one that gets used has changed.

Current (a3\functions_f\animation\interp)

params [["_a", 0.0, [0.0]], ["_b", 0.0, [0.0]], ["_alpha", 0.0, [0.0]]];

_a + _alpha * (_b - _a);

Prior (a3\functions_f_exp_a\math)

params [["_a", 0.0, [0.0]], ["_b", 0.0, [0.0]], ["_speed", 1.0, [0.0]], ["_deltaTime", 0.0, [0.0]]];

private "_result";
_result = 0.0;

if (_a != _b) then
{
    _result = (_a * (1.0 - _deltaTime * _speed)) + (_b * _deltaTime * _speed);
};

_result;

[kymckay]

Good find and fix, I'd say we may as well just make the code inline and remove the call altogether