docs: Escape brackets to satisfy the linkchecker

My change to use `Type::def_id()` (formerly `Type::def_id_full()`) in
more places caused some docs to show up that used to be missed by
rustdoc. Those docs contained unescaped square brackets, which triggered
linkcheck errors. This commit escapes the square brackets and adds this
particular instance to the linkcheck exception list.

library/core/src/str/traits.rs

@@ -234,7 +234,7 @@ unsafe impl SliceIndex<str> for ops::Range<usize> {
 /// Implements substring slicing with syntax `&self[.. end]` or `&mut
 /// self[.. end]`.
 ///
-/// Returns a slice of the given string from the byte range [`0`, `end`).
+/// Returns a slice of the given string from the byte range \[0, `end`).
 /// Equivalent to `&self[0 .. end]` or `&mut self[0 .. end]`.
 ///
 /// This operation is *O*(1).
@@ -304,9 +304,8 @@ unsafe impl SliceIndex<str> for ops::RangeTo<usize> {
 /// Implements substring slicing with syntax `&self[begin ..]` or `&mut
 /// self[begin ..]`.
 ///
-/// Returns a slice of the given string from the byte range [`begin`,
-/// `len`). Equivalent to `&self[begin .. len]` or `&mut self[begin ..
-/// len]`.
+/// Returns a slice of the given string from the byte range \[`begin`, `len`).
+/// Equivalent to `&self[begin .. len]` or `&mut self[begin .. len]`.
 ///
 /// This operation is *O*(1).
 ///
@@ -433,7 +432,7 @@ unsafe impl SliceIndex<str> for ops::RangeInclusive<usize> {
 /// Implements substring slicing with syntax `&self[..= end]` or `&mut
 /// self[..= end]`.
 ///
-/// Returns a slice of the given string from the byte range [0, `end`].
+/// Returns a slice of the given string from the byte range \[0, `end`\].
 /// Equivalent to `&self [0 .. end + 1]`, except if `end` has the maximum
 /// value for `usize`.
 ///

library/std/src/sys_common/wtf8.rs

@@ -686,7 +686,7 @@ impl Wtf8 {
     }
 }
 
-/// Returns a slice of the given string for the byte range [`begin`..`end`).
+/// Returns a slice of the given string for the byte range \[`begin`..`end`).
 ///
 /// # Panics
 ///

src/tools/linkchecker/main.rs

@@ -85,6 +85,8 @@ const INTRA_DOC_LINK_EXCEPTIONS: &[(&str, &[&str])] = &[
     ("core/slice/trait.SliceIndex.html", &["begin</code>, <code>end"]),
     ("alloc/slice/trait.SliceIndex.html", &["begin</code>, <code>end"]),
     ("std/slice/trait.SliceIndex.html", &["begin</code>, <code>end"]),
+    ("core/primitive.str.html", &["begin</code>, <code>end"]),
+    ("std/primitive.str.html", &["begin</code>, <code>end"]),
 
 ];