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 std::num::Saturating

Saturating is an implementation of saturating math operations (at the
moment just add and sub) for integral types.
Update Iterator impls to use Saturating

Replace hand-rolled saturation math with calls to Saturating.

Fix one impl that didn't use saturating math.
Added hexadecimal encoding module

FromHex ignores whitespace and parses either upper or lower case hex
digits. ToHex outputs lower case hex digits with no whitespace. Unlike
ToBase64, ToHex doesn't allow you to configure the output format. I
don't feel that it's super useful in this case.
Some minor hex changes
ToBase64 and ToHex perf improvements

The overhead of str::push_char is high enough to cripple the performance
of these two functions. I've switched them to build the output in a
~[u8] and then convert to a string later. Since we know exactly the
bytes going into the vector, we can use the unsafe version to avoid the
is_utf8 check.

I could have riced it further with vec::raw::get, but it only added
~10MB/s so I didn't think it was worth it. ToHex is still ~30% slower
than FromHex, which is puzzling.

Before:

```
test base64::test::from_base64 ... bench: 1000 ns/iter (+/- 349) = 204 MB/s
test base64::test::to_base64 ... bench: 2390 ns/iter (+/- 1130) = 63 MB/s
...
test hex::tests::bench_from_hex ... bench: 884 ns/iter (+/- 220) = 341 MB/s
test hex::tests::bench_to_hex ... bench: 2453 ns/iter (+/- 919) = 61 MB/s
```

After:

```
test base64::test::from_base64 ... bench: 1271 ns/iter (+/- 600) = 160 MB/s
test base64::test::to_base64 ... bench: 759 ns/iter (+/- 286) = 198 MB/s
...
test hex::tests::bench_from_hex ... bench: 875 ns/iter (+/- 377) = 345 MB/s
test hex::tests::bench_to_hex ... bench: 593 ns/iter (+/- 240) = 254 MB/s
```
Removing space for NULL terminator

String NULL terminators are going away soon, so we may as well get rid
of this now so it doesn't rot.
Removed convenience encoding trait impls

Encoding should really only be done from [u8]<->str. The extra
convenience implementations don't really have a place, especially since
they're so trivial.

Also improved error messages in FromBase64.
Result::get -> Result::unwrap
Add to_ascii_upper, to_ascii_lower and eq_ignore_ascii_case in std::ascii
auto merge of #8231 : SimonSapin/rust/ascii-upper-lower-case, r=cmr

Original pull request: Add str.to_ascii_lower() and str.to_ascii_upper() methods in std::str.
auto merge of #8287 : sfackler/rust/hex, r=alexcrichton

FromHex ignores whitespace and parses either upper or lower case hex
digits. ToHex outputs lower case hex digits with no whitespace. Unlike
ToBase64, ToHex doesn't allow you to configure the output format. I
don't feel that it's super useful in this case.
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.)
auto merge of #8323 : kballard/rust/saturating, r=thestinger

Implement saturating math in `std::num::Saturating` and use it for `Iterator` impls
option.get -> option.unwrap
std: add result.map_move, result.map_err_move
core: option.map_consume -> option.map_move