ofPixels, problem to allocate huge size of pixels.

Hello,

I found a bug in bytesFromPixelFormat.

template<typename PixelType>
static int bytesFromPixelFormat(int w, int h, ofPixelFormat format){
    return w*h*pixelBitsFromPixelFormat<PixelType>(format)/8;
}

this code should be

template<typename PixelType>
static int bytesFromPixelFormat(int w, int h, ofPixelFormat format){
    return w*h*(pixelBitsFromPixelFormat<PixelType>(format)/8);
}

e.g.
to try to allocate 10000w * 10000h, RGBA pixels,
the order of calculation will be
10,000 * 10,000 = 100,000,000
100,000,000 * 32 = 3,200,000,000 <- overflow!!!

Locate the bytesFromPixelFormat function and inspect how its multiplication is evaluated for large dimensions and RGBA formats. Reproduce the 10,000 × 10,000 allocation case, then verify that the calculated byte count no longer overflows and that relevant existing tests pass.