/fp:fast was introducing FP precision problems, and mixing it with some /fp:precise code caused strange game behaviors, DSI exceptions and freezes. This commit should fix most of the issues introduced by 3.0-73 (r95517a97). Thanks to [email protected] for tracking a lot of these Win32 bugs. Fixes issue 4906. Fixes issue 5138. Probably fixes (not tested) issue 5067.