A smattering of fixes

### Build tweaks:
* Tentative fix for autogen.sh passes a bad argument to aclocal
* Disable SSE2 by default, due to gcc misoptimisations; leave it as an option only.
* Remove Dynamic LightsDriver work (LuaDriver backport on the backburner, instead)

### Behavior tweaks:
* Game now continues to run even if it cannot instantiate a loading window

### Bug fixes:
- OpenForWriting would try to write to read-only VFS drivers and fail, losing data