Store embedded fonts widths table more effective

Some non-scientific experiments: A single 8k pdf document with okular adding a simple typewriter annotation with content "aoeu" in approximately the same place grows without this patch to 894k. With this patch, it grows to 649k.

For comparison, if one doesn't embed the widths content at all, the same process grew to 638k

While this isn't ground breaking gains, it is still some improvement.