options: deprecate 'lua' based options/dirs for 'script'

- --lua and --lua-opts change to --script and --script-opts
- 'lua' default script dirs change to 'scripts'
- DOCS updated

- 'lua-settings' dir was _not_ modified

The old lua-based names/dirs still work, but display a warning.

Signed-off-by: wm4 <wm4@nowhere>
vo_opengl: remove quadbuffer/anaglyph stereo 3D rendering

Obscure feature, and I've never heard of anyone using it.

The anaglyph effects can be reproduced with vf_stereo3d. The only thing
that can't be reproduced with it is "quadbuffer", which requires special
and expensive hardware.