Improve QImage::setPixel messages

Qimage::setPixel() will on occasion print some warnings to the console. However this is less than ideal, and they could be made more descriptive.

One message:

QImage::setPixel: Index 144 out of range

This means the pixel value being set is out of range.  It would be nice if it said what it is, o we'd know, oh, I'm cramming  32 bit data into an 8-bit image, or a 64bit into a 32. I'm not even sure what the index or range being referred to are. I set x,y, and a value. If it's not in the color palette, then it should say that. 

Another message:

QImage::setPixel: coordinate (30354,3443) out of range

 This one is a little better, but it'd be nice to know what the valid dimensions are:

QImage::setPixel: coordinate (30354,3443) outside (30354,3442) 

Usually these will be off-by one errors, but could be other causes.

Finally, it would  be really cool if we could somehow have setPixel throw an exception or take bool *ok=NULL, or something so we can interrupt our program (if (!ok) frap into a breakpoint) and find the issue. Tracking these errors down as s they stream to the console hundreds at a time is frustrating. 

Many thanks.