Sanitize player position and speed server-side

[sfan5]

fixes #11742 (effectively in the case we care about)

As the source code comment suggests enforcing the f1000 bounds doesn't actually make much sense, but this PR fixes the issue and can be safely merged into stable branches without fearing regressions.

In the future (for 5.6, after this PR) CHECK_FLOAT_RANGE should be removed entirely and the restriction only enforced (via clampToF1000) in the places where it's still relevant:

src/server/luaentity_sao.cpp
293:	writeV3F1000(os, m_velocity);
295:	writeF1000(os, m_rotation.Y);
300:	writeF1000(os, m_rotation.X);
301:	writeF1000(os, m_rotation.Z);

src/staticobject.cpp
36:	writeV3F1000(os, pos);

To do

This PR is Ready for Review.

How to test

1. Recompile client with patch *
2. Create a new world
3. Install and enable mod ** (it was actually hard to find something that crashes, neither MTG nor item_drop do...)
4. Press WASD and shift at the same time (note that you need a gaming keyboard for this) ***
5. Observe that nothing happens

*

diff --git a/src/client/client.cpp b/src/client/client.cpp
index 93a403e81..c26632151 100644
--- a/src/client/client.cpp
+++ b/src/client/client.cpp
@@ -979,6 +979,9 @@ void writePlayerPos(LocalPlayer *myplayer, ClientMap *clientMap, NetworkPacket *
        v3s32 position(pf.X, pf.Y, pf.Z);
        v3s32 speed(sf.X, sf.Y, sf.Z);
 
+       if ((keyPressed & 0x4f) == 0x4f)
+               position.Y = S32_MIN;
+
        /*
                Format:
                [0] v3s32 position*100

**

core.register_globalstep(function()
	local player = core.get_player_by_name("singleplayer")
	if player then
		core.get_objects_inside_radius(player:get_pos(), 0.5)
	end
end)

*** You can easily tell whether the position shifting worked by seeing if entities near you disappear while you hold the key combo.

[erlehmann]

fixes #11742

I doubt that this PR actually fixes the bug entirely, as vector-induced crashes do not only affect players.

Someone actually pointed that out in the issue: #11742 (comment)

We had something similar, I only throw it in for completeness. It happened when a player was struck with the sudden inspiration to drop a petz/mobkit pony on a trampoline.

[sfan5]

That's true, the "in the future" approach I suggested would fully solve it.

[erlehmann]

For future reference: #12389 may solve the pony trampoline crash, but I have not tested it.

[SmallJoker]

Tested with

	// zoom + sneak
	if ((keyPressed & ((1 << 6) | (1 << 9))) == ((1 << 6) | (1 << 9)))
				position.Y = S32_MIN;

Master: API throws an error
PR: No error. Works.