RMI Silverstone 1975 THR layout AI hints + AI tweaks 0.1

The track needed a AI hints file and then I went a bit deeper and tweaked the original AI with the AI Spline Editor app.

Intended for the THR layout but it should work on the original one too.
(Tested with rss70/f1 classic 1975/acl gtr/acl gtc/berta tornado/rd1 porknose/mckeown 911)

Back-up rmi_silverstone_1975\THR\ai\fast_lane.ai before install


Thanks RMI/THR