Fix lint about type repetition in bounds

Before Rust 1.15 ?Sized could not be used in where clauses.

This reverts commit d2fe1d7 "Refactor for rust 1.6.0 compatibility"
and updates other places that had used that style.

Author: tormol

src/ascii_str.rs

@@ -101,9 +101,9 @@ impl AsciiStr {
     /// assert_eq!(err.unwrap_err().valid_up_to(), 0);
     /// ```
     #[inline]
-    pub fn from_ascii<B: ?Sized>(bytes: &B) -> Result<&AsciiStr, AsAsciiStrError>
+    pub fn from_ascii<B>(bytes: &B) -> Result<&AsciiStr, AsAsciiStrError>
     where
-        B: AsRef<[u8]>,
+        B: AsRef<[u8]> + ?Sized,
     {
         bytes.as_ref().as_ascii_str()
     }
@@ -937,9 +937,9 @@ pub trait AsMutAsciiStr: AsAsciiStr {
 }
 
 // These generic implementations mirror the generic implementations for AsRef<T> in core.
-impl<'a, T: ?Sized> AsAsciiStr for &'a T
+impl<'a, T> AsAsciiStr for &'a T
 where
-    T: AsAsciiStr,
+    T: AsAsciiStr + ?Sized,
 {
     type Inner = <T as AsAsciiStr>::Inner;
     fn slice_ascii<R>(&self, range: R) -> Result<&AsciiStr, AsAsciiStrError>
@@ -955,9 +955,9 @@ where
     }
 }
 
-impl<'a, T: ?Sized> AsAsciiStr for &'a mut T
+impl<'a, T> AsAsciiStr for &'a mut T
 where
-    T: AsAsciiStr,
+    T: AsAsciiStr + ?Sized,
 {
     type Inner = <T as AsAsciiStr>::Inner;
     fn slice_ascii<R>(&self, range: R) -> Result<&AsciiStr, AsAsciiStrError>
@@ -973,9 +973,9 @@ where
     }
 }
 
-impl<'a, T: ?Sized> AsMutAsciiStr for &'a mut T
+impl<'a, T> AsMutAsciiStr for &'a mut T
 where
-    T: AsMutAsciiStr,
+    T: AsMutAsciiStr + ?Sized,
 {
     fn slice_ascii_mut<R>(&mut self, range: R) -> Result<&mut AsciiStr, AsAsciiStrError>
     where

src/ascii_string.rs

@@ -940,9 +940,9 @@ impl<'a> IntoAsciiString for &'a CStr {
     }
 }
 
-impl<'a, B: ?Sized> IntoAsciiString for Cow<'a, B>
+impl<'a, B> IntoAsciiString for Cow<'a, B>
 where
-    B: 'a + ToOwned,
+    B: 'a + ToOwned + ?Sized,
     &'a B: IntoAsciiString,
     <B as ToOwned>::Owned: IntoAsciiString,
 {