Function load_xeto_source 

pub fn load_xeto_source(
    source: &str,
    lib_name: &str,
    ns: &DefNamespace,
) -> Result<(Lib, Vec<Spec>), XetoError>

Load a Xeto library from source text.

Parses the source, resolves names against already-loaded libraries in ns, and returns the library metadata plus resolved specs.