jbuf: use float ratio

[sreimers]

No description provided.

[juha-h]

I tested this PR using

        replaceVariable("audio_jitter_buffer_type", "adaptive")
        replaceVariable("audio_jitter_buffer_delay", "0-20")

        replaceVariable("video_jitter_buffer_type", "adaptive")
        replaceVariable("video_jitter_buffer_delay", "1-50")

and didn't have issues with calls. In video calls I got some of these:

05-21 16:57:03.216 28352 28473 D Baresip+ Lib: video: recv Picture Loss Indication (PLI)

but they probably are not related to this PR.

[sreimers]

Thanks for testing.

05-21 16:57:03.216 28352 28473 D Baresip+ Lib: video: recv Picture Loss Indication (PLI)

Are both clients baresip?

[juha-h]

Are both clients baresip?

Yes, I have tested both using Debian and Android baresips. I get more of those message when network is slower (mobile vs. local WiFi).

[alfredh]

please rebase to main, wait for CI, and merge to main ...