Fix diving controls

[NHogweed]

Forward/backward keys to control pitch and only jump key to move ahead, like in vanilla engine.

[Try]

Hi, @NHogweed !

I've checked Npc::walkMode vs Npc::isDive. There is an issue, that walkMode not accounting dive/water states, while this patch only hides the issue.

[NHogweed]

this patch only hides the issue

Not sure what do you mean. Does an ordinary player complaining about underwater controls need anything more? Why it's so important to rely on walkMode here (and only here, unlike a couple of lines below)?

[Try]

Not sure what do you mean.

You need to be careful with path you committing, and make sure that code you adding is something that make sense.
I think for now I'll take this PR, as a bug report rather, and will push a popper fix

[NHogweed]

You need to be careful with path you committing

This was a reason why I decided to make changes as little as possible to achieve the stated goal and not to break anything else (that can be observed by a player). Anyway, your "philosophically and aestethically correct" fix is here, so there's no point to argue about that anymore. But there are still cosmetic problems with diving:

• when the hero is upside down in the water, it is noticeable that his height rotation axis is out of his model;
• rotation around height axis is not animated, unlike in vanilla game. The animation should be present when swimming as well.