Vendor dependencies

Let's see how I like this workflow.

vendor/bitflags/tests/basic.rs

@@ -0,0 +1,20 @@
+#![no_std]
+
+use bitflags::bitflags;
+
+bitflags! {
+    /// baz
+    struct Flags: u32 {
+        const A = 0b00000001;
+        #[doc = "bar"]
+        const B = 0b00000010;
+        const C = 0b00000100;
+        #[doc = "foo"]
+        const ABC = Flags::A.bits | Flags::B.bits | Flags::C.bits;
+    }
+}
+
+#[test]
+fn basic() {
+    assert_eq!(Flags::ABC, Flags::A | Flags::B | Flags::C);
+}