Upgrade rust/crates/structopt to 0.3.18

Test: make
Change-Id: Ib5d515b0f5e9ac7fdd0f2f8e2f00ecf54dbf63ca
diff --git a/tests/argument_naming.rs b/tests/argument_naming.rs
index e7fe3d5..88b549d 100644
--- a/tests/argument_naming.rs
+++ b/tests/argument_naming.rs
@@ -309,3 +309,31 @@
         Opt::from_clap(&Opt::clap().get_matches_from(&["test", "SECOND_VARIANT", "--foo-option"]))
     );
 }
+
+#[test]
+fn test_lower_is_renamed() {
+    #[derive(StructOpt, Debug, PartialEq)]
+    struct Opt {
+        #[structopt(rename_all = "lower", long)]
+        foo_option: bool,
+    }
+
+    assert_eq!(
+        Opt { foo_option: true },
+        Opt::from_clap(&Opt::clap().get_matches_from(&["test", "--foooption"]))
+    );
+}
+
+#[test]
+fn test_upper_is_renamed() {
+    #[derive(StructOpt, Debug, PartialEq)]
+    struct Opt {
+        #[structopt(rename_all = "upper", long)]
+        foo_option: bool,
+    }
+
+    assert_eq!(
+        Opt { foo_option: true },
+        Opt::from_clap(&Opt::clap().get_matches_from(&["test", "--FOOOPTION"]))
+    );
+}