Disable Eclipse in config file.

# Description:
Although I love the eclipse code to death it has caused us some issues #2176 and it just seems to refuse to work with the MESA + Ati stuff on Linux... so fuck it, here's that disable the eclipse option.

# Fix:
Add an option to the config like `DisableEclipse=1` to disable the eclipse code for the terrain and sky shaders.

# Notes:
I haven't added a toggle button to the options screen, this is just a `config.ini` editing option.
That's not to say we couldn't have a toggle button but I seem to recall someone was rewriting the screen in Lua using the new GUI at some point and I neither want to make that more work nor do I really want this so easily editable.
What do people think?