Make rustdoc aware of the primitive i128 type

Many thanks to ollie27 for spotting all the places.

src/librustdoc/clean/inline.rs

@@ -268,11 +268,13 @@ pub fn build_impls(cx: &DocContext, did: DefId) -> Vec<clean::Item> {
         tcx.lang_items.i16_impl(),
         tcx.lang_items.i32_impl(),
         tcx.lang_items.i64_impl(),
+        tcx.lang_items.i128_impl(),
         tcx.lang_items.usize_impl(),
         tcx.lang_items.u8_impl(),
         tcx.lang_items.u16_impl(),
         tcx.lang_items.u32_impl(),
         tcx.lang_items.u64_impl(),
+        tcx.lang_items.u128_impl(),
         tcx.lang_items.f32_impl(),
         tcx.lang_items.f64_impl(),
         tcx.lang_items.char_impl(),

src/librustdoc/clean/mod.rs

@@ -1595,11 +1595,13 @@ impl PrimitiveType {
             "i16" => Some(PrimitiveType::I16),
             "i32" => Some(PrimitiveType::I32),
             "i64" => Some(PrimitiveType::I64),
+            "i128" => Some(PrimitiveType::I128),
             "usize" => Some(PrimitiveType::Usize),
             "u8" => Some(PrimitiveType::U8),
             "u16" => Some(PrimitiveType::U16),
             "u32" => Some(PrimitiveType::U32),
             "u64" => Some(PrimitiveType::U64),
+            "u128" => Some(PrimitiveType::U128),
             "bool" => Some(PrimitiveType::Bool),
             "char" => Some(PrimitiveType::Char),
             "str" => Some(PrimitiveType::Str),

src/libstd/primitive_docs.rs

@@ -597,6 +597,17 @@ mod prim_i32 { }
 ///
 mod prim_i64 { }
 
+#[doc(primitive = "i128")]
+//
+/// The 128-bit signed integer type.
+///
+/// *[See also the `std::i128` module](i128/index.html).*
+///
+/// However, please note that examples are shared between primitive integer
+/// types. So it's normal if you see usage of types like `i8` in there.
+///
+mod prim_i128 { }
+
 #[doc(primitive = "u8")]
 //
 /// The 8-bit unsigned integer type.
@@ -641,6 +652,17 @@ mod prim_u32 { }
 ///
 mod prim_u64 { }
 
+#[doc(primitive = "u128")]
+//
+/// The 128-bit unsigned integer type.
+///
+/// *[See also the `std::u128` module](u128/index.html).*
+///
+/// However, please note that examples are shared between primitive integer
+/// types. So it's normal if you see usage of types like `u8` in there.
+///
+mod prim_u128 { }
+
 #[doc(primitive = "isize")]
 //
 /// The pointer-sized signed integer type.