Move some Map methods onto TyCtxt.

The end goal is to eliminate `Map` altogether.

I added a `hir_` prefix to all of them, that seemed simplest. The
exceptions are `module_items` which became `hir_module_free_items` because
there was already a `hir_module_items`, and `items` which became
`hir_free_items` for consistency with `hir_module_free_items`.

compiler/rustc_driver_impl/src/pretty.rs

@@ -273,7 +273,7 @@ pub fn print<'tcx>(sess: &Session, ppm: PpMode, ex: PrintExtra<'tcx>) {
                 let attrs = |id| hir_map.attrs(id);
                 pprust_hir::print_crate(
                     sm,
-                    hir_map.root_module(),
+                    tcx.hir_root_module(),
                     src_name,
                     src,
                     &attrs,
@@ -294,7 +294,7 @@ pub fn print<'tcx>(sess: &Session, ppm: PpMode, ex: PrintExtra<'tcx>) {
         }
         HirTree => {
             debug!("pretty printing HIR tree");
-            format!("{:#?}", ex.tcx().hir().krate())
+            format!("{:#?}", ex.tcx().hir_krate())
         }
         Mir => {
             let mut out = Vec::new();