libsyntax/ext/deriving/cmp/* was ignored by the build system.
syntax: make #[deriving(TotalOrd)] lazy.

Previously it would call:

  f(sf1.cmp(&of1), f(sf2.cmp(&of2), ...))

(where s/of1 = 'self/other field 1', and f was
std::cmp::lexical_ordering)

This meant that every .cmp subcall got evaluated when calling a derived
TotalOrd.cmp.

This corrects this to use

   let test = sf1.cmp(&of1);
   if test == Equal {
      let test = sf2.cmp(&of2);
      if test == Equal {
        // ...
      } else {
        test
      }
   } else {
     test
   }

This gives a lexical ordering by short-circuiting on the first comparison
that is not Equal.
std: implement Total{Ord,Eq} for pointers.
Add test for short-circuiting #[deriving(Eq,Ord,TotalEq,TotalOrd)].
auto merge of #8285 : huonw/rust/deriving+++, r=alexcrichton

Some general clean-up relating to deriving:
- `TotalOrd` was too eager, and evaluated the `.cmp` call for every field, even if it could short-circuit earlier.
- the pointer types didn't have impls for `TotalOrd` or `TotalEq`.
- the Makefiles didn't reach deep enough into libsyntax for dependencies.

(Split out from https://github.com/mozilla/rust/pull/8258.)