Introduce VecPerParamSpace and use it to represent sets of types and

parameters

This involves numerous substeps:

1. Treat Self same as any other parameter.
2. No longer compute offsets for method parameters.
3. Store all generic types (both trait/impl and method) with a method,
   eliminating odd discrepancies.
4. Stop doing unspeakable things to static methods and instead just use
   the natural types, now that we can easily add the type parameters from
   trait into the method's polytype.
5. No doubt some more. It was hard to separate these into distinct commits.

Fixes #13564

src/libsyntax/ast.rs

@@ -208,14 +208,6 @@ impl Generics {
     }
 }
 
-#[deriving(Clone, PartialEq, Eq, Hash, Encodable, Decodable, Show)]
-pub enum DefRegion {
-    DefStaticRegion,
-    DefEarlyBoundRegion(/* index */ uint, /* lifetime decl */ NodeId),
-    DefLateBoundRegion(/* binder_id */ NodeId, /* depth */ uint, /* lifetime decl */ NodeId),
-    DefFreeRegion(/* block scope */ NodeId, /* lifetime decl */ NodeId),
-}
-
 // The set of MetaItems that define the compilation environment of the crate,
 // used to drive conditional compilation
 pub type CrateConfig = Vec<Gc<MetaItem>>;