minor update in waveform tool (and a minor fix)

- fix warning in test/common_test.c so that compilation works on newer versions of GCC
- fix some minor typos in the "-h" output waveform tool 
- add a "--border-width" option to the waveform tool

I know those are 3 unrelated fixes, that should've been 3 separate pull requests, but unfortunately my git fu is not that good :( Sorry about that.

I also didn't want to add myself to the copyright notice, but that was the only way to pass the pre-commit hook, so there. I don't mind them, but I wouldn't mind not including them either. 

Hope you can cherry-pick what you want.