codegen: Actually honor the new option for module_lines.
codegen: Actually honor the new option for module_lines.

Only when modules are enabled of course.

emilio/rust-bindgen,rust-lang/rust-bindgen,emilio/rust-bindgen,rust-lang/rust-bindgen,rust-lang/rust-bindgen,rust-lang/rust-bindgen,emilio/rust-bindgen,emilio/rust-bindgen,emilio/rust-bindgen