std: Second pass stabilization for ptr

This commit performs a second pass for stabilization over the `std::ptr` module.
The specific actions taken were:

* The `RawPtr` trait was renamed to `PtrExt`
* The `RawMutPtr` trait was renamed to `MutPtrExt`
* The module name `ptr` is now stable.
* These functions were all marked `#[stable]` with no modification:
  * `null`
  * `null_mut`
  * `swap`
  * `replace`
  * `read`
  * `write`
  * `PtrExt::is_null`
  * `PtrExt::offset`
* These functions remain unstable:
  * `as_ref`, `as_mut` - the return value of an `Option` is not fully expressive
                         as null isn't the only bad value, and it's unclear
                         whether we want to commit to these functions at this
                         time. The reference/lifetime semantics as written are
                         also problematic in how they encourage arbitrary
                         lifetimes.
  * `zero_memory` - This function is currently not used at all in the
                    distribution, and in general it plays a broader role in the
                    "working with unsafe pointers" story. This story is not yet
                    fully developed, so at this time the function remains
                    unstable for now.
  * `read_and_zero` - This function remains unstable for largely the same
                      reasons as `zero_memory`.
* These functions are now all deprecated:
  * `PtrExt::null` - call `ptr::null` or `ptr::null_mut` instead.
  * `PtrExt::to_uint` - use an `as` expression instead.
  * `PtrExt::is_not_null` - use `!p.is_null()` instead.

src/libstd/io/extensions.rs

@@ -22,7 +22,7 @@ use num::Int;
 use ops::FnOnce;
 use option::Option;
 use option::Option::{Some, None};
-use ptr::RawPtr;
+use ptr::PtrExt;
 use result::Result::{Ok, Err};
 use slice::{SliceExt, AsSlice};
 

src/libstd/io/mod.rs

@@ -935,7 +935,7 @@ impl<'a> Reader for &'a mut (Reader+'a) {
 // API yet. If so, it should be a method on Vec.
 unsafe fn slice_vec_capacity<'a, T>(v: &'a mut Vec<T>, start: uint, end: uint) -> &'a mut [T] {
     use raw::Slice;
-    use ptr::RawPtr;
+    use ptr::PtrExt;
 
     assert!(start <= end);
     assert!(end <= v.capacity());