improvement: stop motor sound after crash

[yepyepyep4711]

as a "feature" from the original game, the motor keeps audibly running at full speed after a crash, up until the car is back on the track. I suggest this be changed to stop after the crash effects stop.

[J1mbo]

Adjust ocrash::crash_switch() in ocrash.cpp around line 260 to match as below (add the 'if' section before do_car_flip):

      // Flip Car
        case 2:
            if (config.engine.fix_bugs) {
                oferrari.rev_pitch1 = 0; // mute engine during crash flips
            }
            do_car_flip();
            break;