Rename Rptr to Ref in AST and HIR

The name makes a lot more sense, and `ty::TyKind` calls it `Ref` already
as well.

Author: Noratrieb

src/types.rs

@@ -688,7 +688,7 @@ impl Rewrite for ast::Ty {
 
                 rewrite_unary_prefix(context, prefix, &*mt.ty, shape)
             }
-            ast::TyKind::Rptr(ref lifetime, ref mt) => {
+            ast::TyKind::Ref(ref lifetime, ref mt) => {
                 let mut_str = format_mutability(mt.mutbl);
                 let mut_len = mut_str.len();
                 let mut result = String::with_capacity(128);
@@ -1059,7 +1059,7 @@ pub(crate) fn can_be_overflowed_type(
 ) -> bool {
     match ty.kind {
         ast::TyKind::Tup(..) => context.use_block_indent() && len == 1,
-        ast::TyKind::Rptr(_, ref mutty) | ast::TyKind::Ptr(ref mutty) => {
+        ast::TyKind::Ref(_, ref mutty) | ast::TyKind::Ptr(ref mutty) => {
             can_be_overflowed_type(context, &*mutty.ty, len)
         }
         _ => false,