Add decoder: signature analysis

[sharow]

It is HP's troubleshooting tools.

specification is patented. it is expired now.
https://patents.google.com/patent/US4991175A/en

detail about the Signature Analysis:
https://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1977-05.pdf

sigrok WIKI page draft:
https://hackmd.io/@tEk2WdkmQxG8SHsmxaIqQg/Hke6dUG_H

related PR:

• sigrok-test: signature: add test case sigrok-test#5
• sigrok-dumps: signature: add dumps and README sigrok-dumps#9

[uwehermann]

Hi, sorry for the delay! Merged in 112a264 with a few small whitespace/cosmetic changes squashed-in, thanks a lot!

Added a few commits on top which fix a few additional smaller things.

I've changed the license metadata field to reflect what the license header in pd.py says (GPLv2+), but if you prefer GPLv3+ please feel free to change both accordingly.

I've also grabbed most of the content from your wiki page draft, thanks a lot! Page is here:
https://sigrok.org/wiki/Protocol_decoder:Signature

Is Public Domain fine with you for the content and the PulseView screenshot?

We can't use screenshots from HP manual (or other photos which are not self-made) since we don't own the copyright on those, so they're omitted.

Thanks again for your work on the decoder!

[sharow]

GPLv2+
Is Public Domain fine with you for the content and the PulseView screenshot

Of cause it's fine!

We can't use screenshots from HP manual

ya, sorry it's my mistake.

thanks!!