gitignore: Add cscope files

[vkochan]

No description provided.

[b4n]

Why? Do something in the build system or alike generate them?

[frlan]

Seems to be a common tool in real world. I've just cherry-picked it as it doesn't hurt

[b4n]

I don't think we should add everything to our .gitignore just because it's "common". If some tools spurt out files everywhere and the user cares, he has several means for achieving the exact same goal without convincing every upstream project to add a new ignore rule. One of these solutions is to add such rules in ~/.gitignore. Another is to list those in .git/info/exclude.

So although I don't mind much, I woulnd't have merged this kind of things without sensible reason.

[frlan]

Well, fair point. Will leave this in, but for future request you might true.

[codebrainz]

In the future we could also consider using .gitignore files in each plugin's directory and leaving the root one for global Autotools and Waf cruft.