Add primitive documentation to libcore

This works by doing two things:
- Adding links that are specific to the crate. Since not all primitive
  items are defined in `core` (due to lang_items), these need to use
  relative links and not intra-doc links.
- Duplicating `primitive_docs` in both core and std. This allows not needing CARGO_PKG_NAME to build the standard library. It also adds a tidy check to make sure they stay the same.

library/core/primitive_docs/box_into_raw.md

@@ -0,0 +1 @@
+../std/boxed/struct.Box.html#method.into_raw

library/core/primitive_docs/fs_file.md

@@ -0,0 +1 @@
+../std/fs/struct.File.html

library/core/primitive_docs/io_bufread.md

@@ -0,0 +1 @@
+../std/io/trait.BufRead.html

library/core/primitive_docs/io_read.md

@@ -0,0 +1 @@
+../std/io/trait.Read.html

library/core/primitive_docs/io_seek.md

@@ -0,0 +1 @@
+../std/io/trait.Seek.html

library/core/primitive_docs/io_write.md

@@ -0,0 +1 @@
+../std/io/trait.Write.html

library/core/primitive_docs/net_tosocketaddrs.md

@@ -0,0 +1 @@
+../std/net/trait.ToSocketAddrs.html

library/core/primitive_docs/process_exit.md

@@ -0,0 +1 @@
+../std/process/fn.exit.html

library/core/primitive_docs/string_string.md

@@ -0,0 +1 @@
+../std/string/struct.String.html

library/core/src/bool.rs

@@ -2,7 +2,8 @@
 
 #[lang = "bool"]
 impl bool {
-    /// Returns `Some(t)` if the `bool` is [`true`](keyword.true.html), or `None` otherwise.
+    /// Returns `Some(t)` if the `bool` is [`true`](../std/keyword.true.html),
+    /// or `None` otherwise.
     ///
     /// # Examples
     ///
@@ -18,7 +19,8 @@ impl bool {
         if self { Some(t) } else { None }
     }
 
-    /// Returns `Some(f())` if the `bool` is [`true`](keyword.true.html), or `None` otherwise.
+    /// Returns `Some(f())` if the `bool` is [`true`](../std/keyword.true.html),
+    /// or `None` otherwise.
     ///
     /// # Examples
     ///

library/core/src/char/methods.rs

@@ -96,7 +96,7 @@ impl char {
     /// Converts a `u32` to a `char`.
     ///
     /// Note that all `char`s are valid [`u32`]s, and can be cast to one with
-    /// [`as`](keyword.as.html):
+    /// [`as`](../std/keyword.as.html):
     ///
     /// ```
     /// let c = '💯';
@@ -372,7 +372,7 @@ impl char {
     /// println!("\\u{{2764}}");
     /// ```
     ///
-    /// Using [`to_string`](string/trait.ToString.html#tymethod.to_string):
+    /// Using [`to_string`](../std/string/trait.ToString.html#tymethod.to_string):
     ///
     /// ```
     /// assert_eq!('❤'.escape_unicode().to_string(), "\\u{2764}");
@@ -448,7 +448,7 @@ impl char {
     /// println!("\\n");
     /// ```
     ///
-    /// Using [`to_string`](string/trait.ToString.html#tymethod.to_string):
+    /// Using [`to_string`](../std/string/trait.ToString.html#tymethod.to_string):
     ///
     /// ```
     /// assert_eq!('\n'.escape_debug().to_string(), "\\n");
@@ -502,7 +502,7 @@ impl char {
     /// println!("\\\"");
     /// ```
     ///
-    /// Using [`to_string`](string/trait.ToString.html#tymethod.to_string):
+    /// Using [`to_string`](../std/string/trait.ToString.html#tymethod.to_string):
     ///
     /// ```
     /// assert_eq!('"'.escape_default().to_string(), "\\\"");
@@ -937,7 +937,7 @@ impl char {
     /// println!("i\u{307}");
     /// ```
     ///
-    /// Using [`to_string`](string/trait.ToString.html#tymethod.to_string):
+    /// Using [`to_string`](../std/string/trait.ToString.html#tymethod.to_string):
     ///
     /// ```
     /// assert_eq!('C'.to_lowercase().to_string(), "c");
@@ -1002,7 +1002,7 @@ impl char {
     /// println!("SS");
     /// ```
     ///
-    /// Using [`to_string`](string/trait.ToString.html#tymethod.to_string):
+    /// Using [`to_string`](../std/string/trait.ToString.html#tymethod.to_string):
     ///
     /// ```
     /// assert_eq!('c'.to_uppercase().to_string(), "C");

library/core/src/lib.rs

@@ -130,6 +130,7 @@
 #![feature(decl_macro)]
 #![feature(doc_cfg)]
 #![feature(doc_notable_trait)]
+#![feature(doc_primitive)]
 #![feature(exhaustive_patterns)]
 #![feature(extern_types)]
 #![feature(fundamental)]
@@ -355,3 +356,5 @@ pub mod arch {
         /* compiler built-in */
     }
 }
+
+include!("primitive_docs.rs");