GRIM: Add a config option to disable ARB shaders: "use_arb_shaders", defaulted to true
(cherry picked from commit 61eeb6327818bfbf9b8dfb8ae13d74f09a1c1db6)
DOCS: Document the use_arb_shaders option.
(cherry picked from commit be46bd6151d379c9de1d8b14e040dfa16a9a87a9)