rustdoc: Removed Foreign{Function,Static} item types.

They are just (unsafe) functions and static items to most users
and even compilers! The metadata doesn't distinguish them, so Rustdoc
ended up producing broken links (generated `ffi.*.html`, links to
`fn.*.html`). It would be best to avoid this pitfall at all.

src/librustdoc/html/render.rs

@@ -1495,12 +1495,10 @@ fn item_module(w: &mut fmt::Formatter, cx: &Context,
             ItemType::Enum            => 5,
             ItemType::Constant        => 6,
             ItemType::Static          => 7,
-            ItemType::ForeignFunction => 8,
-            ItemType::ForeignStatic   => 9,
-            ItemType::Trait           => 10,
-            ItemType::Function        => 11,
-            ItemType::Typedef         => 12,
-            _                         => 13 + ty as u8,
+            ItemType::Trait           => 8,
+            ItemType::Function        => 9,
+            ItemType::Typedef         => 10,
+            _                         => 11 + ty as u8,
         }
     }
 
@@ -1559,8 +1557,6 @@ fn item_module(w: &mut fmt::Formatter, cx: &Context,
                 ItemType::Method          => ("methods", "Methods"),
                 ItemType::StructField     => ("fields", "Struct Fields"),
                 ItemType::Variant         => ("variants", "Variants"),
-                ItemType::ForeignFunction => ("ffi-fns", "Foreign Functions"),
-                ItemType::ForeignStatic   => ("ffi-statics", "Foreign Statics"),
                 ItemType::Macro           => ("macros", "Macros"),
                 ItemType::Primitive       => ("primitives", "Primitive Types"),
                 ItemType::AssociatedType  => ("associated-types", "Associated Types"),