Roll speed in "mouse steering" mode is incorrect for nimble ships

[Gorbald]

Increasing the "roll" stat above pi/2 does not increase real roll speed in mouse steering mode.

 

Steps to reproduce:

1. make a ship with Roll 3.14 (take any ship that's not too big and stick some thrusters to it)

2. switch to mouse steering and do a complete 360 degree (2*pi rad) roll (X or Z key by default)

 

Expected behaviour:

it takes 2 seconds

 

Actual behaviour:

It takes 4 seconds