Store ptr_width as u32 on Config

This removes the dependency on IntTy, UintTy from Session.

src/librustc_codegen_llvm/builder.rs

@@ -325,8 +325,8 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         use rustc::ty::{Int, Uint};
 
         let new_kind = match ty.kind {
-            Int(Isize) => Int(self.tcx.sess.target.isize_ty),
-            Uint(Usize) => Uint(self.tcx.sess.target.usize_ty),
+            Int(t @ Isize) => Int(t.normalize(self.tcx.sess.target.ptr_width)),
+            Uint(t @ Usize) => Uint(t.normalize(self.tcx.sess.target.ptr_width)),
             ref t @ Uint(_) | ref t @ Int(_) => t.clone(),
             _ => panic!("tried to get overflow intrinsic for op applied to non-int type")
         };