Function load_xeto_dir 

pub fn load_xeto_dir(
    dir: &Path,
    ns: &DefNamespace,
) -> Result<(String, Lib, Vec<Spec>), XetoError>

Load a Xeto library from a directory containing .xeto files.

Reads all .xeto files in the directory, concatenates them (pragma from the first file that has one), and processes as a single library.