convert region_inference into a module, so I can attach docs

Author: nikomatsakis

src/librustc/middle/region.rs

@@ -15,6 +15,9 @@ pass builds up the `scope_map`, which describes the parent links in
 the region hierarchy.  The second pass infers which types must be
 region parameterized.
 
+Most of the documentation on regions can be found in
+`middle/typeck/infer/region_inference.rs`
+
 */
 
 

src/librustc/middle/typeck/infer/mod.rs

@@ -51,6 +51,7 @@ pub mod combine;
 pub mod glb;
 pub mod lattice;
 pub mod lub;
+#[path = "region_inference/mod.rs"]
 pub mod region_inference;
 pub mod resolve;
 pub mod sub;