xbps-query: add message when no packages have been found

[OfekShochat]

closes #494

[crtxcr]

Just my opinion as another user:

While I too would like to see a message, this PR one is incomplete because:

1. misses a newline at the end of the printf
2. does not apply to -f and is therefore, inconsistent
3. prints to stdout, not stderr

I would argue it should also be shown without -v.

[OfekShochat]

sure. if I change those, will this be done?

[JamiKettunen]

No idea, you'd have to get an actual review from a Void Linux maintainer, in particular @Duncaen seems to be the one merging on this repo.