Fix a couple of issues in from_utf8 docs

Author: ollie27

src/libcore/str/mod.rs

@@ -174,10 +174,10 @@ impl Utf8Error {
 ///
 /// If you are sure that the byte slice is valid UTF-8, and you don't want to
 /// incur the overhead of the validity check, there is an unsafe version of
-/// this function, [`from_utf8_unchecked()`][fromutf8], which has the same
+/// this function, [`from_utf8_unchecked()`][fromutf8u], which has the same
 /// behavior but skips the check.
 ///
-/// [fromutf8]: fn.from_utf8.html
+/// [fromutf8u]: fn.from_utf8_unchecked.html
 ///
 /// If you need a `String` instead of a `&str`, consider
 /// [`String::from_utf8()`][string].
@@ -275,7 +275,7 @@ unsafe fn from_raw_parts_mut<'a>(p: *mut u8, len: usize) -> &'a mut str {
 /// Converts a slice of bytes to a string slice without checking
 /// that the string contains valid UTF-8.
 ///
-/// See the safe version, [`from_utf8()`][fromutf8], for more.
+/// See the safe version, [`from_utf8()`][fromutf8], for more information.
 ///
 /// [fromutf8]: fn.from_utf8.html
 ///