Allow schemes to be listed

kernel/scheme/sys/scheme.rs

@@ -0,0 +1,18 @@
+use collections::Vec;
+
+use scheme;
+use syscall::error::Result;
+
+pub fn resource() -> Result<Vec<u8>> {
+    let mut data = Vec::new();
+
+    let schemes = scheme::schemes();
+    for (name, _scheme_lock) in schemes.iter_name() {
+        if ! data.is_empty() {
+            data.push(b'\n');
+        }
+        data.extend_from_slice(name);
+    }
+
+    Ok(data)
+}