Image clipping area rounding error

Creating images with PDFBox and merging them together when you have two pages that connect will create a white line between the images.

We have looked into the issue and tried to fix it and found that the clipping area is a bit to tight so the images will not be rendered correctly. My guess is that this is due to a rounding error when using floats. 

Most of the graphics functions in java use double precision and PDFBox uses floats so when using layer upon layer of bounding boxes intersecting the clipping area it might get skewed to a bad bounding box.

I've added a patch to this issue with the code we use as a workaround today. It's by no means the final solution to the problem but it resolves the white line issue.

To be sure that you get the error when generating the images use the following command

```
java -jar pdfbox-app-3.0.0-SNAPSHOT.jar PDFToImage -dpi 150 -quality 0.95 -format jpg page-1.pdf
```

We run java 8 on our machines.