Add "DirectX" and "OpenGL" to `doc_valid_idents`
Add "DirectX" and "OpenGL" to `doc_valid_idents`

graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust