Change the low_latency option to a flag

[vladimir-kazakov]

This PR fixes the issue #1224. It changes the low_latency option that takes a boolean value to a flag, which can be used without arguments. If the flag is present, the low latency mode is enabled; otherwise, it's disabled.

[lu-zero]

I like the change

[coveralls]

Coverage remained the same at 82.605% when pulling 73621ed on vladimir-kazakov:low-latency-as-flag into d7599d6 on xiph:master.

[tdaede]

Does it now reject --low_latency true/false? If so I'll need to adjust the AWCY arguments to match.

[rom1v]

Thank you 👍

This is a breaking change from the user point of view, maybe we should increase rav1e version to 0.2.0?

[tdaede]

We don't have a versioning policy yet, so I just made one: #1231

[vladimir-kazakov]

Does it now reject --low_latency true/false?

@tdaede, yes, using any value with a flag leads to an error, because flags don't expect values.

This is a breaking change from the user point of view, maybe we should increase rav1e version to 0.2.0?

I guess the version should change for a specific release, not because of every PR with a breaking change. In other words, it should be okay to have breaking changes in the master (development) branch, but the version number should be increased before making a release.

[rom1v]

I guess the version should change for a specific release, not because of every PR with a breaking change. In other words, it should be okay to have breaking changes in the master (development) branch, but the version number should be increased before making a release.

Yes, absolutely.

[lu-zero]

I guess we could put a label so when we cut releases we won't forget.