Add the notion of a dependency tracking status to commandline arguments.

Commandline arguments influence whether incremental compilation
can use its compilation cache and thus their changes relative to
previous compilation sessions need to be taking into account. This
commit makes sure that one has to specify for every commandline
argument whether it influences incremental compilation or not.

src/librustc/lint/mod.rs

@@ -269,7 +269,7 @@ impl LintId {
 }
 
 /// Setting for how to handle a lint.
-#[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug)]
+#[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash)]
 pub enum Level {
     Allow, Warn, Deny, Forbid
 }

src/librustc/middle/cstore.rs

@@ -73,7 +73,7 @@ pub enum LinkagePreference {
 }
 
 enum_from_u32! {
-    #[derive(Copy, Clone, PartialEq)]
+    #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
     pub enum NativeLibraryKind {
         NativeStatic,    // native static library (.a archive)
         NativeFramework, // OSX-specific