Fix Sound.is_precached and StreamSound.is_precached performance

[jsza]

Fixes #221.

I feel like I'm missing something with this fix, but it works with some light testing.

[jsza]

Would it perhaps be better to implement StringTable.__contains__ on the C++ side?

[jordanbriere]

Hey, thank you! I can see where it was not optimized at all with the iteration. However, an even faster way would probably be to use engine_sound.is_sound_precached.

[jsza]

@invincibleqc Just tested on TF2 and CS:S, it looks like engine_sound.is_sound_precached always returns True for any string. I'll add a comment to the code warning about that.

[Ayuto]

Yep, contains would be the best solution. If the engine function always returns True, we should remove it.

[jordanbriere]

Yes, after searching I found a thread that mentions the issue with is_sound_precached and is the reason why it was switched to use the string tables. Exposing a __contains__ method on the c++ side could be a tiny bit faster but I think the difference from your proposal would be negligible. I went ahead and merged your pull request, thank you!

If the engine function always returns True, we should remove it.

Definitely. But is that method only returning True on OrangeBox games or all engines?

[jordanbriere]

After thinking about it, went ahead and added a __contains__ wrapper directly to the StringTable class because while this PR was fixing this particular case, the performance issue was directly in the string tables implementation.

As for is_sound_precached, I'm tempted to propose wrapping it on the engines affected over removing it drastically.