Add a comment missing from 5aff0e7c

For some reason, I had this comment in my local tree but not in the
branch I sent with the PR.

src/librustc/middle/borrowck/check_loans.rs

@@ -638,8 +638,8 @@ fn check_for_assignment_to_restricted_or_frozen_location(
                 loan_path = match *loan_path {
                     // Peel back one layer if, for `loan_path` to be
                     // mutable, `lp_base` must be mutable. This occurs
-                    // with inherited mutability and with `&mut`
-                    // pointers.
+                    // with inherited mutability, owned pointers and
+                    // `&mut` pointers.
                     LpExtend(ref lp_base, mc::McInherited, _) |
                     LpExtend(ref lp_base, _, LpDeref(mc::OwnedPtr)) |
                     LpExtend(ref lp_base, _, LpDeref(mc::GcPtr)) |